Why Low T3 causes Weight Gain + Symptoms & Treatment Guide

Checking your total T3 and free T3 may be the most important thyroid tests you can look at. 

Unfortunately many physicians aren't even ordering these tests which may lead to a missed diagnosis of low T3 syndrome. 

Fortunately there are several therapies that you can do to increase this important thyroid hormone and take steps to reduce your symptoms. 

If you are experiencing weight gain, chronic fatigue, chronic pain or a slow metabolism then increasing your T3 becomes even more important. 

Let's discuss how to increase these levels and how T3 impacts weight and weight loss...


Why T3 is the MOST important Thyroid Hormone

T3 thyroid hormone is one of the most important thyroid hormones (we will go over the other arguably more important hormone below).

T3 is the active form of thyroid hormone in your body.

It can be measured by testing your total T3 in the serum, and by assessing your free T3 levels.

The total amount of T3 in your body represents all of the T3 in your serum (blood), and the free T3 represents the amount of T3 available to be used and for binding.

​You can think of total T3 as a reservoir for free T3, but both numbers are important. 

But why?

It turns out that all of the beneficial effects of thyroid hormone in your body comes from T3 (NOT T4 thyroid hormone).

T3 thyroid hormone acts directly on the nucleus of your cells via a nuclear receptor to literally turn on your genes and alter genetic transcription.

This is very important because it can help you understand exactly how thyroid hormone works in the body.

The fact that thyroid hormone works on the nucleus of the cell helps to explain why it takes weeks for changes in thyroid hormone to take effect. 

Altering genetic transcription, altering enzyme production and changing cellular transcription takes times. 

These changes in genetic transcription help increase energy, increase metabolism, stabilize hair growth and do all of the functions associated with proper thyroid hormone function. 

  • Bottom line: T3 thyroid hormone does all of the good things that you want thyroid hormone to do. It is the most important thyroid hormone to monitor for this reason. 

Understanding the difference between T4 & T3

The biggest issue with T3 is that most doctors, physicians and endocrinologists don't actually test for it.

​And that's why you need to understand the difference between T4 and T3. 

You're probably familiar with T4 whether you realize it or not:

Some physicians actually test for T4 (so you may actually have your free T4 levels to look at).

Thyroid diet 4 week plan side bar

Even if your doctor doesn't test for T4 and instead uses the TSH only for monitoring your thyroid function, you are probably being treated with a T4 only thyroid medication like Levothyroxine, Synthroid or Levoxyl. ​

​And that's the problem:

T4 is used in the body as a reservoir to be turned into T3 through a conversion process known as T4 to T3 conversion. 

So why is that a big deal?

​Doctors make one big mistake when treating and supplementing hypothyroid patients with T4 only medications:

They assume that your body will take all of that T4 thyroid hormone and turn it straight into T3.

​And, as you can probably guess, that doesn't always happen. 

Instead your body is just as likely to turn it into the anti thyroid metabolite reverse T3. ​

Reverse T3 directly competes for cellular binding with T3 and can actually cause hypothyroid symptoms. ​

So when testing for thyroid hormone and when evaluating if you are being managed correctly it's far more useful to know your T3 levels instead of your T4 levels. 

Make sense? 

Why low T3 leads to Weight Gain

One of the biggest issues that hypothyroid patients face is weight gain.

Part of this problem is mediated by the fact that many patients don't actually convert T4 to T3 efficiently, and the other part is the reliance upon TSH as a measure of proper thyroid hormone in the body.

The truth is that most patients don't actually convert thyroid hormone efficiently AND TSH is not the best marker for evaluating thyroid function in the body. ​

These problems, along with low T3 levels, help contribute to the weight gain and weight loss resistance that many hypothyroid patients face and struggle with. 

The reason T3 is so important for proper weight management is simple:

T3 is one of the most powerful, if not the most powerful, mediators of energy production from your mitochondria. 

These energy production from your mitochondria serve 2 very important functions:

1. Help determine your basal metabolic rate. 

2. Help provide you with a subjective sense of "energy". 

That means that low levels of T3 will directly (or indirectly) result in a slower than normal metabolism (sound familiar?) and may result in the symptoms of fatigue and/or low energy levels. 

Obviously both of these factors are very important for maintaining a normal and healthy weight, but they are almost important for losing weight.

Your metabolism accounts for the majority of calories burned throughout the entire day, so a slow metabolism results in weight gain.

Meanwhile, low energy levels may prohibit you from being able to exercise making weight loss difficult. ​

So what is the solution?​

How to Test your T3 levels

For the reasons listed above (and many others we won't be discussing) testing for your T3 becomes a VERY important part of thyroid management.

​I need to take a second and make a disclaimer here:

​If you have to ask your Doctor for these tests there is a good chance they are NOT going to understand how to interpret them correctly. 

So don't assume that you will get proper treatment for your thyroid problems just by getting these tests done, the testing is really only the beginning.

What matters more than the actual tests is the treatment and management afterwards.

So, while testing is important, don't make the mistake of assuming that your physician or provider will be willing to treat your appropriately once you have the results.

​Ok, back to testing:

These are probably the most important thyroid tests to get if you want to understand how your thyroid is functioning in your body:

  • Total T3
  • Free T3
  • Reverse T3
  • Sex hormone binding globulin

You will probably notice that TSH and free T4 don't even make an appearance, and that is definitely intentional. 

TSH really only gives you an idea of pituitary levels of thyroid hormone and T4 is only somewhat helpful in evaluating thyroid conversion. ​

Instead I want you to focus on getting the labs listed above and then interpreting the results based off of "optimal" levels and not "normal" levels.

When it comes to hormones there is a huge difference between being in the "normal" range and having adequate function and being optimal.

​For instance:

As a 20-40 year old woman, you don't want your free T3 levels to be in the range of an 80 year old. ​

Use ​the sample ranges below to determine if your levels are optimal or not. 

Optimal ranges for the following lab tests (assuming you aren't taking T3 containing thyroid hormone already): 

  • Total T3: Should be in the upper half of the reference range
  • Free T3: Should be in the upper half of the reference range
  • Reverse T3: Should be as low as possible, any number higher than 15 is a problem
  • Sex hormone binding globulin: In men this should be 20-30 and in women it should be 70-80 (this value isn't helpful if you are taking oral estrogen or birth control pills)

​These values assume that you are NOT taking any thyroid medication (if you are, you can't use those ranges) and it assumes that you also are experiencing the symptoms of hypothyroidism

​I want to take a second and point out the value of sex hormone binding globulin:

SHBG helps give you an idea of the tissue levels of thyroid hormone in your liver.

As an aside, you can think of TSH as a marker of tissue levels of thyroid hormone in your pituitary​. 

The liver is a better marker of other tissues in your body because it contains both deiodinases.

The pituitary doesn't contain the deiodinase which turn T4 into reverse T3, which means that ALL thyroid hormone hitting the pituitary will be able to convert just fine.

But that same thing may not be true in other tissues, and that's why SHBG is helpful. ​

Low T3 syndrome + Euthyroid sick syndrome

​Let's say that you have your tests in front of you and you have determined that you do indeed have low T3. 

It turns out that there is actually a name for your condition:

It's known as low T3 syndrome and/or euthyroid sick syndrome.

Almost every doctor is aware of this condition, but they've probably forgot about it overtime (or don't realize its importance outside of the hospital).

The reason is simple:

Low T3 is a compensatory response to harmful stimuli on the body.

thyroid metabolism reset poster for side bar

We can sum it up like this:

Anything in your body that causes high levels of stress, high levels of inflammation, physical/emotional trauma or any other stressor on the body ​may result in this condition. 

Another surprising reason for low T3 is simply being overweight.

Patients who are obese have lower levels of free T3 and higher levels of reverse T3.

​Medications can also reduce the conversion of T4 to T3 including: blood pressure medications, diabetic medications, pain blocking medications, anti depressants and nerve modulators (gabapentin & lyrica, etc.). 

​When you look at all of the potential causes of low T3 that exist, it's easy to see why this condition is becoming more and more common. 

​Nowadays it's not uncommon for people to be overweight, stressed out and already taking multiple medications. 

I should also take a second to discuss that one of the most common causes of low T3 is calorie restriction and a history of yo-yo dieting.

If you've ever done these types of diets in the past there is a very good chance that you not only have damaged your metabolism, but that you have also have low levels of T3. ​

If you fall into this category don't worry - we are going to talk about treatment below:​

Symptoms of Low T3

But first we need to talk about the symptoms of low T3.

If you recall I pointed out earlier that you need the combination of symptoms PLUS low lab values to diagnose low T3 syndrome.

Use this list of symptoms in conjunction with your lab tests to determine if you have low T3:

  • Cold body temperature & extremities (less than 98.0 degrees)
  • Low resting heart rate despite being overweight and non-conditioned (resting heart rate less than 50-60)
  • Weight gain and/or weight loss resistance
  • Decreased energy levels and inability to sustain activity levels for long periods of time (even low intensity exercises like walking cause worsening fatigue)
  • Other hormonal problems including: estrogen dominance, low progesterone levels, insulin resistance and/or leptin resistance
  • Chronic pain and/or chronic muscle tension/cramps
  • Hair loss, hair breakage, dry skin and/or brittle/damaged nails

As you may have noticed this list mimics many of the symptoms with some exceptions...

Many of these symptoms result from a lower than normal metabolism and may directly or indirectly lead to weight gain and weight loss resistance.

In addition to these symptoms you may experience any (or all) of the traditional symptoms of hypothyroidism

It's important to note that the symptoms of low T3 may vary from person to person, but the list above represents the most common symptoms that patients may experience.

Use the list above in combination with your lab tests to determine if you should move on to the next step...

Natural treatment to increase T3 levels

​I'm going to go over how to approach low T3 levels and what you can do about it. 

This is really important because, as I mentioned previously, most physicians don't pay much attention to T3 levels.

This means that they aren't likely to change your medication, increase your dose, or even mention these lab tests to begin with.

It's therefore important that you are knowledgable and do whatever you can to increase your T3 naturally.

I will also go over how to increase your T3 the easy way (taking T3 medication) below. ​

#1. Boost conversion of T4 to T3

One of the easiest ​ways to boost T4 to T3 conversion is by taking targeted supplements to help boost this natural conversion process. 

It turns out that there are several supplements that can help accomplish this goal:

  • Zinc: Zinc has been shown to increase T4 to T3 conversion, act as a powerful anti-inflammatory and reduce oxidative stress. Zinc is also a VERY common nutrient deficiency in the US. Standard zinc supplements also fall short because they don't contain zinc bound to picolinic acid (which is the most absorbable form of zinc). Doses of 30-60mg per day can help boost thyroid conversion if taken with selenium. 
  • Selenium: Selenium can also improve T4 to T3 conversion, act as an anti-inflammatory and help balance the immune system. Selenium is also very helpful for patients with autoimmune thyroiditis or Hashimoto's thyroiditis. Taking 200-400mcg per day (when accompanied with zinc) can help boost thyroid function and conversion. 

#2. Reduce reverse T3 levels

Another indirect way of increasing the effectiveness of T3 levels in the body is by reducing your reverse T3 levels.

Recall that reverse T3 directly competes for cellular binding with T3 levels.

This means the higher the reverse T3 the more free T3 you need to counteract the reverse T3.

By decreasing reverse T3 levels you don't necessarily need to increase T3 levels because it will be easier for the T3 to do its job.

Make sense?

So how do we do it? ​

You have to tackle the main problems that might be causing high reverse T3 levels to begin with.

Use the list below and address any or all of the problems in your body to reduce your reverse T3 levels: ​

  • Lower inflammation: Inflammation from any cause will increase reverse T3 levels and result in decreased thyroid function. You can test for inflammation by checking ESR and CRP. If these are elevated then you should consider taking anti inflammatory supplements like Turmeric, Krill oil with astaxanthin and quercetin + bromelain
  • Treat SIBO or other GI related problems: Treating your GI tract is very important for managing thyroid conversion because the gut is the place of at least 20% of the conversion process. This is further complicated by the fact that many conditions like SIBO, IBS, GERD and SIFO reduce conversion by increasing inflammation and reducing the conversion efficiency in the gut. Approximately 50% of thyroid patients have concurrent SIBO/SIFO whether they realize it or not, you can learn more about treating and managing SIBO here
  • Lower insulin: High insulin levels (and also high blood sugar levels) inhibit the T4 to T3 conversion process and contribute to weight gain. If your fasting insulin is greater than 5.0 you should aggressively treat and manage your levels with supplements + dietary changes. If you have insulin resistance (or high blood sugar) consider using the following supplements: Alpha lipoic acid, Berberine and chromium
  • Lower leptin levels: Leptin is another hormone that contributes aggressively to weight loss resistance and is missed by most physicians who either don't know how to treat it, or don't understand its importance in managing thyroid levels and managing weight loss. I've written extensively about how to test for and manage leptin resistance and you can read more about that here
  • Stop dieting and consciously limiting your calories: If you are consuming less than 1,500 calories per day just to maintain your weight you are damaging your metabolism and contributing to low T3 syndrome. In order to heal your metabolism it will be necessary to STOP consciously reducing your calories to halt and reverse this process. 

Reducing reverse T3 levels can be quite complex and may require some digging to get to the bottom of your specific problem. 

#3. Increase thyroid hormone production

Another round about way to increase T3 levels indirectly is by increasing your total thyroid hormone production.

This doesn't always work by itself, but if used with techniques designed to both boost T4 to T3 conversion AND reduce reverse T3 levels it can be particularly effective.

It turns out that over 10 different supplements are required for proper thyroid hormone production.

If you are deficient in any of these nutrients then you may suffer with decreased thyroid hormone production over time leading to worsening symptoms of hypothyroidism. 

You can find the full list of supplements required in this post as well as how to test for and determine which supplements you may need to take. ​

​T3 thyroid medication therapy

​Now let's talk about the easy way to increase T3 (well relatively easy way). 

Simply taking T3 can automatically provide a boost to your T3 levels and significantly (and usually quickly) reduce any symptoms you may be having from low T3.

We ​touched on medications previously, so it's worth discussing them a little bit more in detail. 

Part of the reason that so many patients feel terrible despite taking thyroid medication has to do with the conversion process of T4 to T3.

You already know that most physicians prescribe T4 only medications like synthroid, levothyroxine and levoxyl.

What you may not realize is that these T4 only thyroid medications may be converted into reverse T3 instead of the T3 you want it to turn into.

So, in some cases, you might actually be making your symptoms worse by taking thyroid medication.

In some cases you may be fueling the fire by providing your body with more substrate to produce reverse T3 with.

​So how do you deal with this problem?

This problem can be dealt with by reducing (or eliminating) the amount of T4 hormone you are taking and instead providing your body with T3 only thyroid medication.

If you give your body direct T3 there isn't any substrate to produce reverse T3 from so these levels will automatically drop. ​

Getting your physician to prescribe T3 only medication can be difficult however, so this may not work for everyone - but if possible it's certainly worth a try.

Better yet - the combination of all of the natural therapies listed above with T3 only thyroid medication is very effective. ​

NDT vs Liothyronine/cytomel for Low T3​

What about natural desiccated thyroid hormone, where does NDT fit into all of this?

As you may know NDT is predominately a T4 thyroid medication, but it does contain some T3 in it as well.

The ratio is in favor of T4 about 3:1, however, which means that NDT can also contribute to reverse T3 production.

In some cases dropping the total dose of NDT may be required to flush out reverse T3.

In addition some patients do quite well with the combination of NDT + T3 medication. ​

Recap + Final thoughts

Having low T3 is a serious problem that tends to be ignored or under appreciated by most physicians. 

Because T3 thyroid hormone is the active thyroid hormone in your body it is the most important thyroid hormone to evaluate. 

If you are experiencing any of the symptoms of low T3 syndrome or euthyroid sick syndrome make sure that you get the following lab tests: free T3, total T3, reverse T3 and sex hormone binding globulin. 

If you find that you have low T3 then a combination of natural treatments plus changing your thyroid medication may be in order. 

Remember that when it comes to improving your thyroid function it will likely require a combination of therapies to achieve the best results. 

Now it's your turn:

Do you have low T3?

What have you done to increase your T3 levels?

What has worked for you?

Leave your comment below and I will personally respond. 

Dr. Westin Childs

I'm Dr. Childs and I write these posts. I'm a physician that specializes helping patients lose weight, have more energy and FEEL better. My practice focuses on hormone imbalances, thyroid issues and weight loss resistance. My goal is to provide the BEST information out there on the internet that is both actionable and trustworthy. Get my free ebook: Hashimoto's Diet Guide here. You can also find more about my personal journey back to health here.

Click Here to Leave a Comment Below 48 comments
Ryan - January 27, 2017

Hello! Awesome article! Thank you for providing this information in such a clear manner. I was diagnosed with Hashimoto’s after my first son was born 6years ago. I was placed on a T4 only medication which I have been taking since (hopefully this will change soon ;). I have recently started my Hashimoto’s educational/improvement journey. I asked my primary care doctor to order the lab tests mentioned in this article, along with some you have mentioned in other articles. He obliged and I am still waiting for the results. There are optimal ranges for lab tests mentioned, if you are not taking any thyroid medication. What are the optimal ranges for lab tests if you have been taking thyroid medication? Thank you!

    Dr. Westin Childs - January 27, 2017

    Hey Ryan,

    I will have to create a different post entirely on that subject because it can be very confusing if not explained correctly. Right now I don’t have that information available on my site.

      Ryan - January 27, 2017

      Sounds good Dr. Childs! I am looking very forward to reading it when available! Thanks!

Nim K - January 28, 2017

I have been on t4 since past 4 years but i did not loose any weight at all though i exercised 3-4 times a week, last year my i started t3 (100mcg) on my own after researching and it made me lose about 15 pounds in a span of 3 months with reglular weight training 6 days a week, now the problem is i am on t3 since past 8 months but i am again not losing any weight and i am weight training regularly, i also included clenbuterol for about 2 months ( 2 weeks on 2 weeks off ) but i am not at all losing weight and i am getting depressed because of this, should i start T4 or T3? What is the exact dosage i i start t3 again? Please help me doctor.


    Dr. Westin Childs - January 28, 2017

    Hey Nim,

    There is no exact dose or “perfect” dose to be used as a standard. I use various doses for various patients based on a number of factors including history and lab tests.

Aysha - January 28, 2017

Hi Dr Childs,

I love how you make these subjects so easy to understand especially the importance of reverse T3. Fingers crossed I’ll be starting T3 soon.

However, I am wondering whether to reduce T4 slightly when introducing a low dose of T3 as I’ve heard some people do this or should I stick to the current T4 amount and just add a small amount of T3?

Is RT3 the reason why some people do this?


Brenda Rapoport - January 30, 2017

Thank you so very much for your advice and information. I’ve been stuck in ‘T4 dr. syndrome’ for over a decade and with your advice i am hoping to enlighten my present dr. regarding the need for t3. First, of course, there are the tests for such, which i will ask him to do. I cant thank you enough for your kindness, caring and incredible knowledge and insight. Ive been 70 lbs overweight all this time due to thyroid medications that are not helping me at all. Wish me luck.

    Dr. Westin Childs - February 5, 2017

    Hey Brenda,

    As a general rule, if you have to ask for the right tests then your doctor probably isn’t going to be able to help you. Interpreting the test results and treating is 95% of the equation.

DEE - January 30, 2017

Hi I have low t3 and im medicsted with levothyroxine. I take all the mentioned supplements but is there some product that can build up t3 alone? Thanks.

lyndsey - January 30, 2017

Hi I was diagnosed with postpartum thyroiditis and now suffer with hypothyroidism I am on T 4 after reading up about it I tried T3 which I brought privately and felt loads better so I went to the doctor to ask if they can prescribe me T 3 and the doctor said point blank NO and that they are not allowed to prescribe it! Is that right surely if that’s what you need they should give it you. The doctor looked like she knew it was wrong she even said it could be to do with cost and advised me to buy it privately.

Rubiya - January 30, 2017

Hi Dr.Childs,
I’ve been hypothyroid for 13 years, was put on 175 mcg T4, it never helped in relieving my symptoms. After reading your blogs, last year I discussed the T3 issue with my doc and thankfully got referred to a very cooperative Endocrinologist who immediately put me on 50 mcg pure T3. But my brain was wired all the time on T3, I had spikes of energy in the morning followed by terrible mid day crashes, hair loss and insomnia and most importantly I wasn’t losing weight at all, instead I gained 30 lbs during transition period! My bloods on 50 mcg pure T3 was THS= 0.4 which is optimal & free T3= 7.7, which is above normal range so it doesn’t make sense why did I not feel better & why did I gain weight ?
Had my endo appointment last month and he adviced me to try T4/T3 combo instead, so now I’m taking 40 mcg T3 & 50 mcg T4, feeling a lot better already on the combination but still not losing any weight, so my endocrinologist gave a go ahead for me to start an extreme calorie restricted diet (800 cals/day) but it’s medically supervised so I know I will lose weight safely but I’m worried about my metabolism! They did do a breathing test to check my metabolism before
the diet & it turned out that my body is only burning 1350 calories/day which is not exciting at all but, Just wanted to ask you that as now I’m on more T3 will it damage my metabolism any further? Or if I’ go back on T3 only medication, the calorie restricted diet shouldn’t have any effect on the metabolism anyway or will it?

Len - January 30, 2017

What would cause high sex binding hormone? My T3 and T4 are low normal and my RT3 is 15. I have low normal Testosterone and normal estrogen levels. My sex binding hormone has been really high for years and the doctors act like it’s no big deal.

Kaye - January 31, 2017

I am on Nature Thyroid, an NDT, but I suspect that I have low T3, based on weight gain, fatigue, and very low resting heart rate. What levels should I be looking at in a thyroid panel, since I’m on NDT?

Marina - January 31, 2017

Dear Dr. Childs,

Thank you so much for all your advice and free-of-charge information. The more I learn about thyroid issues and hormone imbalances, the angrier I get at all the doctors who treated me falsely or not at all during my entire life. My parents took me to a medically supervised weight loss program for the first time when I was ten years old. The doctors put me on a high-carb diet with tightly restricted calories (though I was not extremely overweight at the time, just somewhat chubby). And they did all this without running even a single tiny test on my thyroid, insulin, other hormones or any physical reasons for weight gain whatsoever. I was ten years old, I was active, played outside a lot, and still no one cared to check if there might be something wrong with my hormones or metabolism. At age 22, I went to my GP and asked him to check my thyroid because I had all the symptoms (and I was about 190 lbs at the time). He ran the tests, then of course told me everything was normal… Today at age 27 I’m 270 lbs and I know for sure that I have Hashimoto’s, insulin resistance as well as leptin resistance (my serum leptin is 64). I also most likely have PCOS and have had it for a very long time (since before puberty). ALL OF THIS I found out by my own research, not one single doctor I consulted ran any blood test on me that I didn’t specifically ask for. But still, and this makes me furious: The whole world still thinks it’s okay to blame ME ALONE for being obese, that it’s okay to fat-shame me and discriminate me. After all this time, my hormonal disorders have become so complex and so severe that I have given up on trying to fix them. (I live in Germany, no Dr. Childs around here sadly.) If I’d been diagnosed and treated correctly when I was a child, I’m sure most of my current issues wouldn’t have developed at all. But still, no one blames the doctors who have failed to help. No one understands that I am not lying when I say I can’t lose weight. My own mother still believes that I’m lying to her face and it breaks my heart. I just wish the media would finally stop painting a false picture and instead make it clear that a whole lot of people have medical conditions which lead to obesity and that, to this day, the bigger part of our physicians are unable to effectively treat these conditions. You, Dr. Childs, are one of the very few, but most precious exceptions and that’s why I just want to say: Thank you.

Barbara - January 31, 2017

Hi, been hypothyroid & on 100mcg for 20+ years. Got prescribed t3 15 years ago,which I think helped,but British NHS cancelled these prescriptions. Have struggled on but seem to have hit a crisis, NHS increased my thyroxine dose then reduced it back again as I wasn’t feeling good.Another year on I feel terrible so got private blood panel,tsh 0.01 t4 total 16.0. Free t4 7.97. Free t3 2.02. I would appreciate your thoughts,due to see same endo in a few weeks who suggests pituitary issue? Thank you

    Dr. Westin Childs - February 5, 2017

    Hey Barbara,

    Make sure you get a full thyroid lab panel, it’s difficult to manage patients without the full picture.

      Barbara - February 7, 2017

      Hi,Dr Westin,appreciate your response.My blood panel on 9th Jan 17 reads:

      TSH 0.01
      T4 Total 16.0
      Free T4 7.97
      Free T3 2.02

      lab suggests I get my pituitary checked. I feel I’ve aged 10 yrs in the last month.Very concerned re cognitive decline over last few years,I’m 67 . Thanks again

gina - February 5, 2017

Great article! I am on NDT and T3, however still have symptoms of hypothyroidism. You provided lab values, however stated they are not to be used if already on T3. What labs should I go by to determine if I may need additional NDT or T3? Thank you!

    Dr. Westin Childs - February 5, 2017

    Hey Gina,

    Currently I don’t have any posts going over that information because it’s more complicated than most people realize, and most lab values I provide are prior to taking thyroid medication (which is where most labs are actually helpful).

Amy - February 5, 2017

Could Low T3 be what triggered my weight loss when I stopped taking my Levothyroxine? I was in school at the time and had no insurance, so I quit taking my Levothyroxine and lost over 60 lbs in about 8 months. Now I’m back on Levothyroxine, I’ve gained all the weight back, am struggling to lose weight, and have no energy.

Michelle - February 6, 2017

I am on levothyroxine but still feel terrible. Constantly tired and no energy. My doctor tested all the labs you listed and said my t3 is good and my antibodies are high which means it’s an autoimmune disease. I have read there are many people that labs say they are good but still have symptoms of hypothyroid. Could this be possible that I’m having symptoms if the t3 is ok?

    Dr. Westin Childs - February 6, 2017

    Hey Michelle,

    Yes, it could also be for a variety of other reasons as well. It’s best to be evaluated and treated by someone who is knowledgable in this area.

Heather - February 8, 2017

Great explanation of a complicated issue! I desperately need a doctor that can help my 16 year old son with these issues. I went to your website and see that you are not taking new patients. Can you make any suggestions on where I might find a doctor who knows about/believes in this condition and is willing to treat it?

    Dr. Westin Childs - February 8, 2017

    Hey Heather,

    Unfortunately I don’t know of any other doctors who practice like me (I’m sure they are out there, I just don’t know them). All of the information you see here is self taught, gained through experience and practice, etc. There is no training course for physicians to learn these techniques.

Andy Sullivan - March 1, 2017

I am a 69 year old male. 5’11” 290 lbs. They removed half of my thyroid 8 years ago. It was not cancerous but they did not like the way it looked. I have been on Levothyroxin since then because they do not want the other half to work. the levels that they check are always fine but I cannot lose weight no matter what I try.

Mubashir - March 11, 2017



I know for a long period of time that I have Hashimoto-Hypothyroid however in my country doctors do not seem to know what to do apart from giving Levothyroxine for lifetime.

Currently I am taking (Eltroxin – Levothyroxine) 200mcg daily. Just got my fresh tests done as follows. Reverse T3 testing facility is not available in my country:

Anti-Thyroid Peroxidase….274 IU/mL…..(Ref Range given: less than 35 IU/ML)

Serum Anti Thyroglobulin…<20 IU/ml…..(Ref Range given: Less than 40 IU/ML

Serum Free FT3…2.80 pg/ml….(Ref Range given: 2.1–4.4)

Serum TSH….0.950 ul/ml…(Ref Range given: 0.4–4.2)

Serum FT4…..1.28 ng/dl…..(Ref Range given: 0.89–1.76)

Serum Testosterone….522.2 ng/dl (Ref Range given: 249–836)

Serum TIBC….379 ug/dl…..(Ref Range given: 250–400)

Serum Ferririn…226 ng/ml….(Ref Range given: 28–365)

With an abnormal Anti TPO and Free T3 on the lower side, do you think it would good idea to start Cytomel? My currently problem is: for long I am trying to loose FAT but not achieving.

    Mubashir - March 14, 2017

    Dear Dr.Childs,

    I await your reply.


Wendee Valentine - March 14, 2017

My 16 yo was prescribed T3 in August and saw weight loss and energy increase fairly quickly. She is still struggling significantly however. She is also celiacs.
I can’t get any endocrinologists in Utah to look at her because her TSH and T4 are in normal range. Our primary doctor says she’s probably just over doing things. Should I get her to a gastroenterologist to work on her celiac symptoms, in case leaky gut is the problem? I hadn’t even thought of the correlation until I stumbled on this article.

    Dr. Westin Childs - March 14, 2017

    Hey Wendee,

    Lots of factors may be at play, but addressing GI issues if present would be a good first step. I wouldn’t go to a gastroenterologist for help with increased intestinal permeability, however – as far as they are concerned she is considered cured as long as she is gluten free.

Wendee Valentine - March 14, 2017

Thank you. You are the first physician to take me seriously in six months. Three endocrinologists refused our doctor referrals, and the fourth said the thyroid problem is a “mothers fantasy she needs to get over.” This without ever seeing her. Now I just need to learn how to heal leaky gut!


aimee baylor - April 9, 2017

Dr Childs,

If you’re T3 and T4 are low, RT3 high, Insulin resistant and on Metformin can you take T3?
And can high T3 lead to insulin resistance or make it worse?
So do you have to check your levels every few weeks and when you hit optimal T3 and your RT3 lowers do you stop the T3? Or titrate down?
If you eat right and exercise during this time then should the weight loss (assuming you lost weight) be stable? Or once you’re off T3 can everything can come back?

Kim - April 18, 2017

I’m a 48 year old woman who has suspected low thyroid for some time now….I am experiencing hair loss, cold sensitivity, low basal body temperature, cracked heels, tiredness, and I have extreme difficulty losing weight but gain weight very easily. Last week, my doctor ran a thyroid panel and found my T4 to be normal, but T3 to be low. He prescribed 5 mcg of cytomel to start, with a follow up visit in a couple of months. Is there anything else you recommend that I do?
Thank you,

Gail - April 21, 2017

What would you recommend for a child who has this issue with T3? Doctors are widely unwilling to prescribe anything but T4 for kids. It sounds like increases in T4 may only serve to drive up the need to make higher levels of T3 to combat RT3 production ? TIA

Sherry Forslund - April 22, 2017

I request a RT3 test be done when I had all of my annual physical tests done and I was told No by the and we heatedly discussed to where she agreed. Also argued about ferritin test an she ended up agreeing to that although I was told I wasn’t eating properly if I had an iron issue

I got the call that my test results are “normal” but oh by the way a entire large hospital in SE Michigan does not run RT3 tests as they do not see the need so it was not done. Although the tests were”normal” they were not optimal and I have been gaining more weight so I will start to adapt to some of the supplements recommended here — I have every single sypmtom on this list and my ends wants to remove my cytomel —

Btw Ferritn was not normal and I need to supplement-

Bottom line – education of yourself is your best defense. Doctors see you couple of times a year for minutes at a time and do not know more about your body than you do

Theresa - April 22, 2017

I fought for 23 years to be put on a T3 thyroid med. From day one of diagnosis of Hashimoto’s it was nothing but extremely painful long lasting muscle cramp and weight gain. I gained 65 pounds 2 weeks after diagnosis and stayed that weight for 11 year till breaking my leg from a muscle cramp that lasted 13 hours. I was a very very strong woman lifting 500 pounds with coworkers, after diagnosis I became crippled after any exercise or doing my very strenuous job. Fast forward to in 2012 I stopped breathing cause my T3 was too low! Because of my lifetime of Asthma I fought to start breathing by trying to use diaphramatic breathing exercises. And the worse part was that when we got to the ER there was no way to get any thyroid levels checked quickly. At the time I was on Tirosint 120mg I had been on every single synthetic on the market getting progressively worse. In 2013 as my endocrinologist was calling to give me current labs he finally took note that my T3 was very low. It took an argument to get me on Armour, I had cleaned my toaster over and 3 days later I was cramping from head to toe! As we are treating the T3 instead of the TSH I’m doing better, I’ve had set back from a job I had ….and taking longer to rebound, as I’m now type 2 diabetic, and have ankylosis spondylitis, as well as morphia scleroderma, and lichen sclerosus et atrophicus. I’m on 180mg of Armour now, slowly coming back, unemployed, I just don’t get why doctors don’t listen.

    Dr. Westin Childs - April 22, 2017

    Hi Theresa,

    The environment is such that it’s potentially harmful if a doctor steps outside of the box and practices the way I am discussing here. They will always revert to the safer approach usually because of the risk of litigation.

Barbara - April 22, 2017

Dear Dr. Westin,

reading your article, I can clearly see I am the case of low T3. My TSH and T4 was normal, but T3 below normal levels. I now take T4 + T3 and feel hudge improvement. My question is what does it mean when SHBG is too high? You mentioned it is very important but you did not explain what it means when it is not within the ranges. My Total T3 is 50% and FT3 80%.

I would be very gratefull for your answer!

    Dr. Westin Childs - April 22, 2017

    Hi Barbara,

    High SHBG indicates your thyroid dosing is too high, you have too much native estrogen, or you are supplementing with an oral contraceptive or oral estrogen derivative.

      Barbara - April 23, 2017

      Thank you so much for your answer! I do not take any synthetic estrogen, only natural estrogen cream as my estrogen level is very low… I will decrease my T3 dose in that case. Especially that my TBG is too low, which as I have read also indicate too much thyroid hormones…

      One more thing I forgot to ask, what does it mean when RT3 is below normal levels? I could not find such information enywhere…

Leah - April 26, 2017

Hi Dr. Childs,

I live in Singapore where doctors are not allowed to prescribe T3. I have all of the symptoms of hypothyroidism (weight gain, high cholesterol, depression, poor circulation) with normal labs except for Free T3 that falls in the lower part of the normal range.

Free T3: 4.2 pmol/L (Reference Range 3.5 – 6.5)
Free T4: 1.1 ng/dl (Reference Range 0.71 – 1.85
TSH 0.78 uIU/ml (Reference Range 0.55 – 4.78)

Do you think I should pursue treatment outside the country?

Thanks for your time and help.

Kamela - April 26, 2017

How do I find an actual doctor who looks at all these things and understands the actual optimal ranges and how it all works together? Anyone in Southern California you could refer me to?

Lisa H. - April 26, 2017

Hi Dr. Childs,
Thank you so much for this article!!
My TSH, T4, and Free T3 are all at the bottom end of normal range, but my Total T3 is low at 58. I have typical low t3 symptoms and hypothyroid symptoms. I saw an endocrinologist who told me that I am just fine and that there is nothing wrong with me or my thyroid.
On one hand, sure, that’s great to hear, but on the other hand, then why is my Total T3 so low and why do I feel so bad? (and why do we run tests if we are just going to ignore abnormal results?)
Should I not be concerned about the low total t3?
Unfortunately, I don’t have many options. The endo won’t do anything, therefore the fam doc won’t do anything. I will try your suggestions in this article.
Thank you so much.


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