The TSH Tests your Thyroid Function… Or Does it?
This is actually a fairly contentious topic but we are going to dive in headfirst.
There are many doctors, and patients included, who believe that the TSH is the single best way to assess thyroid function in your entire body.
I am going to argue that this is completely false and that using the TSH is not only unhelpful for thyroid patients but that it also leads to serious problems in thyroid management.
Patients who rely solely on the TSH as a means to determine whether or not their thyroid is actually functioning well will find themselves being undertreated and continuing to suffer from hypothyroid symptoms despite having “normal” levels.
You may have been told by your current doctor or endocrinologist that the TSH is the ONLY test that you need to evaluate your thyroid and if you were told that, you aren’t alone.
But today I am going to talk about a better way to look at the TSH test in the setting of those with existing hypothyroidism.
You are going to learn:
- Why TSH testing fails to actually test for thyroid function
- What TSH levels you should be aiming for
- Why an “optimal” level is not the right way to look at your TSH
- How I look at the TSH when determining how much medication thyroid patients should be on
- And more
Let’s jump in…
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Why Hypothyroid Patients get Frustrated with the TSH
Remember:
This article is dedicated to people who already have low thyroid conditions such as hypothyroidism or Hashimoto’s thyroiditis.
If you do not have a known diagnosis of hypothyroidism or Hashimoto’s then you would want to look at this article about TSH instead.
Interpreting the TSH level in people who are taking thyroid medication is much different compared to people who are NOT on any thyroid medication.
Back on topic.
Thyroid patients often get incredibly frustrated with their doctor when it comes to TSH.
Why?
Because their doctor is constantly trying to tell them that their TSH is normal even though they are experiencing low thyroid symptoms such as fatigue, weight gain, constipation, etc.
How can you experience low thyroid symptoms while simultaneously being told that your thyroid is “fine”?
Something doesn’t make sense here. Either you are lying (which is obviously not true) or your doctor is wrong when they say that the TSH is a measure of thyroid function.
And, unfortunately, it’s not that you are lying but that your doctor is wrong.
To further complicate the picture, the reference provided for interpreting TSH is incredibly broad.
The standard reference range that your doctor will use to determine if your TSH is “normal” typically ranges from around 0.5 to 5.5 (or something similar).
And your doctor will consider you “normal” if you are anywhere in this range.
Many thyroid patients have realized that this range is far too broad and have found that narrowing the range may help improve how people feel.
This has led to the “optimal” ranges that you see so frequently floating around (you can read more about what I mean by optimal thyroid lab ranges here).
But there’s a big problem with that method as well:
It doesn’t take into account individual variability among thyroid patients.
While it’s generally a good idea to narrow the reference range and shoot for a tighter TSH reference range, you can still run into problems with this approach.
Instead of favoring this “optimal” range that so many thyroid patients are shooting for, I recommend using guidelines to help you determine where your TSH should be.
These are the same guidelines that I use when I treat thyroid patients and they have helped me to treat and manage thyroid conditions in hundreds of thyroid patients.
What is a Normal and Healthy TSH Level for Thyroid Patients?
A healthy TSH level for people taking thyroid medication is much different from those people who are checking to see if they have thyroid problems initially.
A healthy TSH level is somewhere in the range of 0.2 to 2.5.
This is a good measure to use if you are just trying to figure out how you compare yourself to healthy adults.
But we cannot as easily use this reference range if you are taking thyroid medications.
Why?
Because thyroid medications interfere with the TSH system and cause suppression of that system.
In addition, we know that taking thyroid medication and lowering your TSH does not automatically mean that your free thyroid hormone levels are optimized.
And in terms of impacting how you feel, your free thyroid hormone levels are much more important than your TSH.
What to Aim For Instead:
As I mentioned above, instead of focusing on an optimal TSH range you should consider these GOALS.
These goals give you more leeway in what range your TSH should fall into.
They also give you leeway outside of the standard reference range which is going to be required to help EVERYONE feel better.
There are some people who will feel great with a TSH of 2.0 and other people who feel great with a TSH of 0.1.
Figuring out where you fit can be complicated but these guidelines should help get you there:
#1. A TSH Level of more than 2.5 is a problem.
The first thing to know and understand is that the highest you would ever want your TSH to be is around 2.5 (1).
There will always be a small percentage of people who feel great with a TSH higher than this 2.5 range but this percentage represents less than 1% of the total.
For the other 99% of people, consider a TSH of 2.5 to be the highest you would ever reasonably want your TSH to go.
Why this range?
Because you are unlikely to see a HEALTHY adult with a HEALTHY thyroid gland ever have a TSH higher than this 2.5 range.
And as a thyroid patient taking thyroid medication, you want to ensure that your thyroid function closely approximates the same level that someone with a healthy thyroid gland would have.
So regardless of the amount of thyroid medication that you are taking, aim to make sure that your TSH is no HIGHER than 2.5.
#2. A low TSH is Okay if you have hypothyroidism and if you are taking thyroid medication.
We just talked about the high end of the reference range and now we are going to focus on the low end of the reference range.
Some thyroid patients are scared to go below that normal range because they believe that if they do they will automatically become hyperthyroid.
This isn’t true.
A low TSH does NOT automatically guarantee that you are in a hyperthyroid state.
In fact, there are a great many thyroid patients with a low TSH who still remain HYPOthyroid with all of their hypothyroid symptoms to prove it.
On the flip side, you have some people who believe that a low TSH isn’t a problem at all and they almost intentionally suppress their TSH.
This isn’t true either but we will talk more about that in a minute.
What’s important to understand here is the difference between a LOW TSH and a suppressed TSH.
A low TSH is any TSH level that is NOT suppressed but which is under the low end of the reference range provided on your lab tests.
Here is an example:
The reference range provided in this example ranges from 0.350 to 5.500.
In this example, any TSH value UNDER 0.35 would be considered “low”.
A suppressed TSH is defined as any TSH level which is undetectable by standard lab testing assays and is usually reported as a value that is less than some specified amount.
If your TSH is suppressed it will come back as < 0.005 or < 0.001 or something similar.
What you need to understand here is that there is a big difference between a LOW TSH and a suppressed TSH.
There have never been reported consequences of a LOW TSH but this isn’t true of a suppressed TSH (more on that below).
The bottom line?
Don’t be afraid if your TSH is low (but not suppressed) and, in fact, this may be something that you want to aim for.
I know from experience that many thyroid patients feel really good when their TSH is flagged as “low” on their lab tests.
The more thyroid medication you take the lower your TSH will go until eventually it becomes suppressed.
If possible, try to get it as low as possible until you feel better and before it becomes suppressed.
#3. A suppressed TSH is probably okay for a short period of time.
The last thing you should understand is that even though suppressing your TSH is not necessarily desirable, it may not be as bad as you are thinking.
As I mentioned before, some thyroid patients believe that a suppressed TSH is of no consequence and may even be desirable.
This is definitely not true as suppressing your TSH absolutely does come with some risks (2).
But those risks may be worth risking depending on your situation.
Consider these examples:
Example #1. A thyroid patient who is 100 pounds overweight.
If there’s an argument to be made for suppressing the TSH it definitely makes sense in the setting of weight loss.
We know for sure that being 100 pounds overweight will increase a person’s risk of diabetes, cancer, heart disease, stroke, and more.
We also know that suppressing the TSH with certain thyroid medications is much more likely to help her LOSE weight.
In my opinion, it makes sense to temporarily suppress her TSH to help her lose 50+ pounds to permanently decrease her risk of these conditions.
Yes, she will experience some increased risk from the TSH suppression but I would argue that this risk is much less than the guaranteed risks she would experience from being 100 pounds overweight.
Example #2. Treatment-resistant bipolar disorder or depression that is negatively impacting your quality of life.
In this situation, we have someone who is suffering from severe depression and bipolar disorder which has negatively impacted her quality of life and may increase her risk of side effects such as suicide.
TSH suppression in these cases, especially with medications such as T3, can dramatically improve both depressive and bipolar symptoms and, in some cases, even reverse them.
I would argue that reducing these depressive symptoms is of paramount importance as the side effects of severe depression may lead to loss of life through suicide.
So doesn’t it make sense to deal with the consequences of TSH suppression for this benefit?
Example #3. A Pre-menopausal woman with severe hypothyroid symptoms that impact her quality of life.
Lastly, there’s a strong argument to be made for TSH suppression in any woman who is pre-menopausal.
It appears that the younger you are, and if you are still menstruating, that the side effects of TSH suppression such as osteoporosis and atrial fibrillation are essentially non-existent (3).
So if you are a pre-menopausal woman AND you are suffering from severe quality of life issues then TSH suppression may be worthwhile.
I absolutely believe that there are some situations in which TSH suppression is beneficial and in which the benefits outweigh the potential consequences.
But, before you suppress your TSH, you better be completely aware of these consequences so you know what you are getting into.
You should have a discussion about the risks versus the rewards with your doctor before jumping in.
Final Thoughts
Optimizing your TSH levels in hypothyroidism is not as easy as you might think.
Instead of focusing on an “optimal” value, I would recommend focusing on THESE guidelines:
- Keep your TSH lower than 2.5
- Don’t worry about a LOW TSH
- A suppressed TSH may be okay in certain circumstances
These guidelines are the same guidelines I use when helping thyroid patients and they have allowed me to help hundreds of thyroid patients feel better and take control of their life.
I should also point out here that even though the TSH has value, there are other thyroid tests that should also be ordered.
These tests include free T3, total T3, free T4, and reverse T3.
If you aren’t able to get these tests then you can at least use the guidelines in this article to help manage your thyroid function.
Now I want to hear from you:
Are you struggling to get your TSH level optimized?
What was your most recent TSH level?
How are you feeling at that level?
Are you planning on trying to push your TSH even lower? Are you planning on suppressing your TSH?
Leave your questions or comments below!
I am STRUGGLING!! Diagnosed with follicular thyroid cancer in 2015. Followed by a TT. Diagnosed hypothyroidism. Changed Dr. 7/8 times since. NO Dr. I’ve found tests rT3’s & they only look at TSH… never felt “optimal” … Lately, I’ve been working out regularly 40 min walk with a weighted back pack followed by light weight training. Also I am following the Keto diet…where I read that I may be limiting my carbs too much as a person diagnosed with hypothyroidism… I must be doing this weight loss stress reduction thing ALLL WRONG… I just had labs done by my PCP & found out my cholesterol was high and that my TSH was a “7”CRAZY LOW!! No WONDER I’m tired by 6:00pm Daily… My current endo & I don’t have a great relationship as we only see each other annually, she’s my 7th Endo doc. & I am So hard TRYING TO LOOSE WEIGHT earnestly! PLEASE HELP!! I am at my wits E N D!! I am scheduled to see my Endo actually today… but I know she more over specializes in diabetes not thyroid health. I’d appreciate your assistance PLEASE!! I am at my highest weight at 267. I am a care giver to my father who is dealing with stage 4 cancer. I N E E D a personal win P L E A S E! Gaining control of my weight gain would be awesome for me personally, as it’s affected my life & self esteem. H E L P!! P l e a s e!!
Hi Doc, Just perusing your site. It refreshing to read your thoughts on thyroid issues versus traditional doctors who look at TSH values and tell you everything is great but you feel like shit.
I’ve been dealing with hypothyroidism for almost 20 years. My values have gone up and down. When this all started and I had a value of 2.0 I felt great. As I aged it started to climb and considered within normal range. At one point it hit 7.50 and the doc upped the dose as I had complained of various symptoms. Well I was put on 100mgs of levothyroxine and had been on it for about 7 years . 2 years ago I was very sick with diarrhea for 11 days and when the doc did blood work my FT4 was on the highest value but she said normal. Since then I have had at least 19 different symptoms of being over medicated. Finally I went to the doc in July and my TSH. Aloe came back as 0.05 and FT4 was 2.84. Doc dropped the dose to 75mg. Been almost 2 months and still having a few different aggravating symptoms. My TSH value one month after dropping the dose came back at 1.84. I’m concerned about my prognosis as this has been going on for at 2 years or more be over medicated. Will I feel good again?
yes, my Dr kept me severely debilitated for 3 years due to focusing on the TSH and T4 only and not my hypo symptoms. Even worse he was one of those Drs that runs the full thyroid panel every 6 months yet didn’t look more closely despite my growing symptoms.
Three years ago my TSH was 1.4 along with normal T4 and T3 levels and he would say my T4 was too high when my TSH was 1.4….what.
Three years later my hypo symptoms are debilitating and my TSH drops to 0.76 but my T4 is 1.6 and T3 is 2.6……..and he says again that my T4 is too high and tries to drop it! Clearly he didn’t understand that my TSH has nothing to do with how I’m feeling.
With all the science based information out there it’s just plain negligence to not identify a person’s symptoms as hypo and offer the correct treatment, especially when they have very little thyroid tissue left and there is no question about whether they have hypothyroidism.
DR CHILDS:
My Status: I HAVE A DEAD THYROID – RADIOACTIVE IODINE TREATMENT FOR GRAVES DISEASE OVER 40 YEARS AGO.
How do I respond to things you discuss on your site?
Example: You recently dealt with iodine and how it can help or hinder the function of your live thyroid.
What should I know about iodine in my diet with a dead thyroid?
I have many questions such of this one.
Is there any resource for people like me, with a dead thyroid.
Henry Goodson
HW.Goodson@Charter.Net
(817) 319-5104
PS I use your T3 Conversion Booster – What should I know about it’s use with no thyroid?
Hi Henry,
Pretty much all of the information you find on my website that pertains to those with low thyroid pertains to you as well. Once your thyroid has been irradiated you are now functionally hypothyroid so all of that information becomes relevant. As an example, T3 conversion booster is great for those post RAI because these people (like yourself) still need to convert T4 to T3.
Hello,
First a little history: Total thryoidectomy in 1987 due to papillary carcinoma with some lymph node involvement. On Synthroid from 1987 to 2018. Now happily taking NP Thyroid. I won’t bore you with the story behind the change since it is the classic “doc not listening” saga.
My last round of lab tests indicate TSH suppression (<.005), but my other lab results are pretty close to your optimal range:
FT3-3.7
FT4-1.19
Reverse T3-13.9
Total T4-6.5
Total T3-133
All of the above are in the Functional Medicine Optimal Range according to my nutritionist. So many ranges to consider, I'm not sure what to go by…
I feel pretty good on a NDT dose of 2 grains, but my doc is concerned about my TSH which makes me want to take some action.
Along these same lines I've read various things about timing of blood work in terms of last medication dose- such as waiting 18 hours, fasting vs. non-fasting, coffee no coffee, etc. I would love to know your thoughts.
Thanks in advance!
My TSH is now5.52. I felt better when it was 2.8
Free t4 is1.36
Free T3 is4.2
Thyroid peroxidaseAB is less than 10IU/ml
I feel I need to have my dose increased. I have always felt better when the TSH is 1 or less
I just received lab back. It shows my TSH at 34.90
I take synthroid 125 mcg daily. Is it possible to go that high? I plan on getting tested and getting all your recommended tests. Any advise in the meantime?
Hi Becky,
Yes, it’s possible for the TSH to go that high and even much higher. If you are taking thyroid medication and it’s that high it means that something probably interfered with the test, you aren’t absorbing the medication, or you are severely resistant to the medication itself.
Hi Dr. Childs, you don’t know how much you’ve enlightened me! I knew nothing about deciphering my thyroid bloodwork… You are a miracle for me!
Ok so my last bloodwork after going from 30mg to 60mg of Armour really concerned me when I went from historically within 0.5-1.0 range TSH to a shocking .08. that along with historically low FT4 (0.9-1.2 range) and low FT3 (2.1-2.6 range). It kicked me over the edge to seek more understanding to figure out what was going on. However it sounds like such a low TSH is not necessarily terrible. I am 30-40# overweight and I did feel good on 60mg since it helped me drop and keep of about 12lbs. Does continuing on 60mg armour, despite the low TSH, seem like a right path?
Hi April,
I can’t provide you with any medical advice over the internet but I would point you to this resource which explains why it probably isn’t a big deal for most people: https://www.restartmed.com/low-tsh-vs-suppressed-tsh-on-thyroid-medication/
Hi, I am exhausted trying to balance my thyroid levels. If my tsh comes back between 0.4-4 our labs don’t bother to check ft4, or t3. I have been hypothyroid for 28 years. It’s a juggling act!! On 200mcg my tsh went to 0.007 and my heart was constantly racing. Over the last few years I’ve been reduced to 125″mcg but TSH now at 2.2 which has caused 35lb weight gain, cold, constipation and breathlessness. I have to ignore docs and up my dose as they just don’t understand the impact.
Why aren’t they more informed??
Best wishes, Siobhan
Hi Siobhan,
Please see this article which explains why doctors are not well informed when it comes to thyroid management: https://www.restartmed.com/endocrinologist-for-thyroid/
Hi Dr.child’s, I was diagnosed with Hasimotos 3yrs ago and I am taking 1/2 of a 5mg tablet of Methtimazole a day. Recently my lab tests changed except my TSH it stays at .015 , freeT3 1.78 freeT4 1.27 thyroid peroxide AB 3.9. ThyroglobulinAntibody,S 1.8 Thyrotropin Receptor, AB 4.69 Does this suggest Graves’ disease? What supplements can I take to help? I am worried about my heart health. Thank You,Paulette Pasquale
Hi Paulette,
By itself, it doesn’t necessarily suggest Graves’ disease but someone definitely thinks you are hyperthyroid because you are taking anti thyroid medication (methimazole). You would only be taking a thyroid blocking medication if someone thought your thyroid was too high at one point.
Hi Dr. Childs,
My blood test result from May 2022 is:
TSH 1.43 (0.3-4.5)
T4 0.90 (0.7-1.5)
T3. 2.30 (1.7-3.7)
Thyroperoxidase Ab. 535
My endocrinologist prescribed me Synthroid, 25mcg because she thought T4 is low.
Do you agree with her?
Thank you
I’m 66 healthy woman and have never had any symptoms of thyroid issues. Went to get annual check and got blood tests. Just got them back:
TSH. 4.08
T4, free. 1.0
T3, free 2.9
Doc says I’m hypothyroid. I feel fine. No weight gain, no constipation, etc. should I take meds or use iodine supplements
Hi Pam,
If you are not feeling symptomatic then starting with thyroid support supplements would be a good idea. You can always retest your thyroid lab tests in a few months to see how you are doing as well.
You can find a list of hypothyroid support supplements here: https://www.restartmed.com/thyroid-supplements/
Hello,
I am 52 yrs old, I have know I idea if I am finished with menopause or this is its last hoopla. I have not had a period in 3yrs. I stopped taking all medications 12 mons ago. 5 mons ago I started feeling stressed and overwhelmed. Thinking it was due to the upcoming family functions graduations and family visits I figured it would settle down after the season was over. Oh no, I could not stop crying over every single thing and then become so angry at myself for crying over stupid things. The self loathing was overtaking me. Went to the doc she was surprised that I had voluntarily stopped all medications including my thyroid meds, she had my blood work done.
The results were TSH is 15.9 which she said was high. From what I am reading, (I do not know if it is a T-3 or 4) Doc put me on .50 mcg of Synthroid. I feel way better the boo hoos have subsided. I just tear up now, and no more loosing my crap 10x a day. So, am I Hypo or Hyper. Will I loose weight now? It is very confusing and I have done research to understand but still lost.
Thank you for reading!
Hi Brigette,
There are many factors that influence your ability to lose weight and your thyroid is one of those. It’s possible that once you start taking thyroid medication it will be easier to lose weight but there is no guarantee as other factors could be contributing as well (including menopause).
Hi Dr. Westin,
I have Hashimotos and have been seeing a holistic practitioner for the past 1 1/2 years to get my thyroid under control. I had been on Levothyroxine for over 20 years. New doctor took me off of Levo and put me on dessicated thyroid. One year into this I began to have hyperthyroid symptoms and my blood work showed a TSH of 0.005, Free T4 & Free T3 out of range on the high end. Doctor took me off of all thyroid supplements and desicated thyroid. All numbers have slowly fallen back into optimal ranges with the exception of my TSH which remains 0.005. I’m feeling good, but am concerned about my thyroid being suppressed. Any recommendations? Thank you!
Hi Carolyn,
I would recommend reading this article for more information on TSH suppression: https://www.restartmed.com/suppressed-tsh/
My doctor has changed my original 200 mcg dose of Levothyroxine multiple times over the past four years based on low TSH, but with no typical symptoms of hyper or overmedication. The first time she lowered it to 175 mcg I developed iron deficiency anemia with a ferritin level going from 40 to 6 within seven months. Blood loss was ruled out, and adding iron raised my ferritin to 25, but I was still feeling hypo symptoms of weight gain, fatigue, etc. Going back to 200 mcg plus iron my ferritin went back up to 42, my weight stabilized, my fatigue improved and I felt great, but my TSH went down to 0.1. So back down to 175 plus iron and my ferritin dropped down to 17, I gained 7 lbs and felt exhausted, but my TSH did increase but was still low at 0.2. (Note: I have always taken the iron 4-5 hours after my LT4.)
She doesn’t agree with my thoughts that I may simply need a higher dose to improve my iron status, and wants to lower my dose further. (I do have other factors that may influence my iron absorption, such as extensive diabetic neuropathy, numerous autoimmune disorders and I am on immunosuppressants post kidney/pancreas transplant.) Increasing my iron supplementation has led to increased nausea and constipation, but only a slight increase in ferritin, which remains at the lowest end of “normal”. I realize I will always have to take iron, but is it possible that the lowered LT4 dose is a main factor for the iron deficiency and that the higher dose may be justified despite the low TSH?
Hi Dr. Childs,
I am newly diagnosed with Hashimoto’s and have a TSH level of 2.8. Despite having symptoms of fatigue, hair loss, weight gain, and cold hands/feet, my endo said I am within normal limits therefore she would not treat me. Furthermore, she said she has no “medical explanation” for my symptoms and suggested that I might be depressed. I just purchased the Hashimoto’s Ab Rx and the Thyroid B Complex to get started. Should I also consider a supplement to lower my TSH level?
Hi Cynthia,
The unfortuate truth is that doctors take the “sit and wait” appraoch to Hashimoto’s by letting your own body destroy your thyroid gland until you are sick enough to need thyroid medication. The biggest issue with this approach is that early disease is when Hashimoto’s is most receptive to natural treatments like supplements. In your case, I would be as aggresive as possible with diet, lifestyle, and supplements in an attempt to put your condition into remission.
In terms of supplements, I’d recommend using as many supplements in this bundle as possible: https://www.restartmed.com/product/hashimotos-bundle/
They should be combined with diet, exercise, stress reduction, and other lifestyle changes as well.
Thank you for your reply Dr. Childs!