Cytomel Side Effects: Complete List & Dosing Guide

Cytomel Side Effects: Complete List & Dosing Guide

Cytomel is the most powerful thyroid medication which means that it can also have some powerful side effects. 

If you’re taking Cytomel and wondering if you are experiencing side effects then sit tight because we are going to dive into everything you need to know about this medication. 

For instance…

Did you know that Cytomel can help with weight loss but that it can also cause hair loss in certain patients?

Unfortunately, many doctors aren’t used to prescribing Cytomel so many patients are left to figure it out for themselves. 

And that’s why I created this guide – to help: ​

  • People who have just started taking Cytomel
  • People who have been taking Cytomel and are wondering if their side effects are caused by the medication itself or by some other cause
  • People who are curious to know if Cytomel can be used to help them improve their quality of life
  • People who want to know if this medication will help them with weight loss
  • People who are struggling with hair loss and believe it may be due to their medication
  • Those who just want to know more about Cytomel, how it works, why it’s different, and what benefits it provides to the body

Positive Side Effects of Cytomel

First off:

If you didn’t already know, Cytomel is a thyroid medication used to treat people who have a sluggish thyroid. 

But that’s not all it can do. 

It can also be used off-label to treat certain psychiatric disorders such as treatment-resistant depression and treatment-resistant bipolar disorder. 

For now, we are going to focus on how it helps to treat the thyroid but much of this information will be relevant to you regardless of why you are using it. 

Cytomel is the brand name for the generic T3 medication known as liothyronine, but both medications contain the same active ingredient known as triiodothyronine

It’s most frequently used to treat the following conditions:

And what you need to know about Cytomel is this:

It is the active form of thyroid hormone, meaning that it is the most powerful thyroid medication you can take. 

As a quick primer:

T3 is the active thyroid hormone while T4 is considered to be the inactive thyroid metabolite. 

Both are technically ‘active’ in the body but T3 is hundreds of times more active than T4 (1). 

It should be differentiated from other thyroid medications like Armour thyroid, Nature-throid, WP thyroid, levothyroxine, and Synthroid.

One thing you need to understand about thyroid medications is that generally, you should NOT be experiencing negative side effects when you take these medications. 


Because, presumably, you are taking the hormone to replace a deficiency inside of your body. 

If all you are doing is replacing that deficiency then you shouldn’t experience negative symptoms only positive effects. 

Assuming you aren’t reacting to any of the fillers or binders in the medication itself and you are on the right dose of thyroid medication for YOUR body, then several things should happen:

Basically, all of the symptoms you were experiencing due to hypothyroidism should be improving, not worsening. 

If you are experiencing any other symptoms (especially negative side effects) then that may be an indication that you are reacting to the fillers or binders in the medication or that your dose is not correct.

We will talk about how to find out if your dose is too high or too low, but for now, we will focus on what to do if these fillers or binders are causing you side effects. 


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The Complete List of Thyroid Lab tests:

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Inactive Ingredients in Cytomel

All medications contain a combination of both active and inactive ingredients. 

The active ingredient is the ingredient that causes all of the physiologic benefits of the medication. 

In this case, the active ingredient in Cytomel is triiodothyronine or L-T3. 

The inactive ingredients help to stabilize the active ingredients and act as a carrier to prevent the breakdown of the active ingredient (2) in the stomach and so on. 

They also are added to change the color, shape, or consistency of the capsule/pill. 

The problem with these inactive ingredients is that certain patients may actually negatively react to them. 

This may put you in a situation where you don’t react to the active ingredient (because you need it) but you may be reacting to the fillers/binders/inactive ingredients in the medication. 

And determining what you are reacting to can be difficult at times. 

For reference, Cytomel contains the following inactive ingredients:

a complete list of inactive ingredients found in the off-white cytomel tablet which are all underlined.
  • Calcium Sulfate
  • Gelatin
  • Starch
  • Stearic Acid
  • Sucrose
  • Talc

It’s been my experience that many patients who use Cytomel and react negatively to it, are often reacting to inactive ingredients, especially starch or gelatin. 

The good news, if you are one of those people who react negatively to the fillers, is that it is possible to compound the active ingredient into a formulation that contains fewer inactive ingredients. 

Formulations such as sustained-release T3 can be created by compounding pharmacies. 

It should be noted, however, that even the sustained release T3 formulation is not without faults. 

Sustained release T3 (or SR T3) contains high amounts of methylcellulose (3) which can also cause similar problems and reactions in certain patients.

Bottom Line: If you are having negative reactions to Cytomel it may not be due to the active ingredient but instead due to the inactive ingredients.

The Complete List of Side Effects of Cytomel

This list will break down all of the possible reactions you may be experiencing while using Cytomel. 

When it comes to side effects there are 3 main categories that you want to be looking at:

  • Hypersensitivity reactions
  • Overdosing
  • Underdosing

Each category comes with a set of unique symptoms and understanding where you fit can help you determine if you need to switch medications or simply alter your dose. 

1) Hypersensitivity Reactions

Hypersensitivity reactions are fairly common and can range from mild to severe, depending on the person. 

These symptoms tend to come from the inactive ingredients, fillers, binders, preservatives, and dyes in the medication. 

a list of serious adverse reactions that cytomel can cause which would warrant seeking medical advice.

Symptoms of hypersensitivity to Cytomel may include: 

  • Rash, hives, or itching
  • Swelling of the Face or extremities
  • Tingling sensation in the hands or face
  • Nausea or vomiting
  • Headaches
  • Difficulty breathing (rare but serious)
  • Tightness in the chest (rare but serious)

If you experience any of these symptoms, and if they persist even after changing or altering your dose, then you may need to switch medications entirely. 

Your best options may be to switch to the generic liothyronine medication or switch to a compounded SR T3 formulation

2) Excessive Dosing

Perhaps more common than hypersensitivity reactions are those reactions caused by the dose of the medication itself. 

Cytomel, as the most powerful T3 medication, is prone to causing symptoms that may mimic hyperthyroidism if used in high doses. 

These side effects are potentially very serious and if you experience any of them you should seek advice from the provider who gave you the medication. 

Their presence indicates that you will need to adjust your dosing or go off of your medication completely. 

In many cases, however, you may be able to simply adjust your dose downward to eliminate them. 

Sometimes, even though the dose may be appropriate, you may be extra sensitive to small increases in T3. 

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You can prevent some of this by simply increasing your dose in a slow and controlled manner. 

A slow titration upwards may prevent symptoms such as heart palpitations, anxiety, and so on. 

If symptoms persist despite lowering your dose then make sure to check your nutrient status and make sure your adrenals have been addressed. 

Symptoms that may indicate your Cytomel dose is too high include: 

  • Rapid heart rate (This is why I recommend tracking your heart rate while taking Cytomel or liothyronine)
  • Tachycardia
  • Irregular heart rate
  • Palpitations (Sensation of rapid heart rate but heart rate remains normal)
  • Shortness of breath
  • Sensitivity to heat
  • Weight gain <—– Rare, but can happen
  • Hair loss <—– Typically temporary but sometimes it can persist
  • Increased sweating 
  • Jittery sensation or increased anxiety 
  • Dizziness or lightheadedness
  • Chest pain or chest discomfort
  • Diarrhea or loose stools
a highlighted list of adverse side effects that can occur with liothyronine which can mimic the symptoms of hyperthyroidism.

3) Insufficient Dosing

Last, but still important, is the idea that you may be on the right medication but your dose may not be high enough. 

If you experience symptoms from this condition then it’s important to realize that these symptoms are not caused by the medication itself but by a deficiency in thyroid hormone in your body. 

The symptoms that indicate your dose is not high enough include the same symptoms that correlate with hypothyroidism. 

The persistence of symptoms such as fatigue, weight gain, constipation, hair loss, and depression may be an indication that you need to continue increasing your dose. 

Will Cytomel Help Me Lose Weight?

​I’ve written extensively on this topic before and you can check out the entire post here

But in the meantime let’s cover some basics:

Yes, Cytomel and liothyronine can absolutely help you lose weight – but only if used correctly and for the right reasons.

Even if you didn’t want to take my word for it after treating hundreds of patients you can take a look at this study as a reference (4):

a highlighted study which outlines the metabolic effect of liothyronine treatment in hypothyroidism.

In this study, patients were either given T3 (Cytomel or liothyronine) or T4 (Synthroid or levothyroxine). 

These patients were given ‘dose equivalents’ of each medication as measured by their TSH. 

Basically, they gave both groups enough thyroid hormone to normalize their TSH down to the same level which was somewhere between 0.5 and 1.5 U/mL. 

The researchers found that those who took equivalent doses of LT3 had reduced body weight and better cholesterol levels without experiencing any negative side effects. 

Those who took T3 lost an extra 4-5 pounds without making any changes to their diet or lifestyle (highlighting the impact that thyroid hormone has on the metabolism)

the conclusion and results from the a study which are highlighted.

Similar results have been found in other studies which compare T4 medications to thyroid medications that contain T3. 

So, given that they tend to work better than T4 why do most doctors fail to prescribe Cytomel?

Much of this has to do with their lack of knowledge on the topic and the fact that they haven’t seen these new studies. 

This allows for a unique opportunity in which you can bring these studies to your doctor to see if they will be willing to give them a try. 

Even though Cytomel can help with weight loss doesn’t necessarily mean that it’s right for everyone. 

Many patients are extremely sensitive to the T3 in Cytomel and it may cause side effects like heart palpitations, anxiety, or panic attacks. 

In addition, you shouldn’t use Cytomel for weight loss if you don’t have hypothyroidism

Doing so may put excess strain on your body, heart tissue, and other organ systems. 

Bottom Line: Cytomel can help with weight loss, but it should be used cautiously because it is a powerful thyroid medication. 

Can Cytomel Cause Weight Gain?​

While it doesn’t make any logical or intuitive sense that Cytomel could cause weight gain, I have seen it happen in a handful of patients. 

In addition, it is also listed as a potential side effect of the medication:

highlighted text showing that weight gain is a potential side effect of using cytomel.

You can take comfort in knowing that this side effect happens very rarely and I’ve only seen it a handful of times. 

With an occurrence of about 1% or less, it’s not a side effect that you should worry about before you consider using this medication. 

It’s not clear to me why Cytomel would cause weight gain but I suspect it’s likely a reaction to a filler or binder within the medication itself. 

I believe this to be the case because all the patients I know who have gained weight on the medication still experienced an improvement in their hypothyroid symptoms and they only experienced a mild weight gain of 3-5 pounds. 

This would lead me to believe that the medication is still working to enhance thyroid function in their body and that the weight gain is caused by some other variable. 

If you do gain weight on Cytomel it is worth switching to SR T3 to see if the problem still persists or switching to Natural Desiccated Thyroid if that fails.  

Cytomel and Hair Loss

One of the main symptoms that patients with hypothyroidism struggle with is hair loss. 

And, I don’t want to alarm you here but Cytomel can actually make hair loss worse

Don’t let this scare you away from trying this medication though, because the hair loss associated with it is only temporary. 

In some patients (around 10% by my estimation) Cytomel can temporarily make hair loss worse for about a 3-4 month period. 

The good news is that this hair loss is temporary and should resolve on its own without any intervention on your part. 

highlighted text which shows that a less serious side effect of cytomel is hair loss.

The problem with this symptom is that it may stop certain people from continuing with their medication because they don’t know that it’s temporary. 

No one really knows for sure why it causes worsening hair loss but I believe it may be due to an increased demand on the hair follicles which is exacerbated by other nutrient deficiencies. 

You can imagine a scenario in which there is a strong signal sent through your body that triggers the growth of hair, but unless you have the building blocks to create the hair it may make the problem worse. 

Something similar may occur in individuals who suffer from hair loss when starting Cytomel. 

If you fit into this category then you’ll want to take certain hair growth nutrients including zinc (5), selenium, iron, and so on. 

You can find a list of reasons why thyroid patients experience hair loss and how to fix them here

If your hair loss persists after 3-6 months and after replacing all of your nutrient deficiencies then it may be time to consider other options.

In these cases, it’s best to lower the dose of Cytomel or switch to SR T3 or NDT if possible. 

How to Find the Right Cytomel Dose for Your Body

​When starting any medication it’s important to realize that your dose will depend on YOUR body. 

That means you shouldn’t base your dose on what has worked for other people.

You may need more or you may need less.

In my practice, the average dose of T3 varies from 5-50mcg with some people needing even less than 5mcg and some needing more. 

​To find your optimal dose I recommend using a combination of these four areas when titrating:

#1. Your Thyroid Lab tests

Whenever you make any changes to your thyroid medication you should always follow and take stock of what is happening to your thyroid lab tests

These lab tests reflect the serum changes of thyroid hormone in your body and they can tell you if what you are doing is working or not. 

When starting Cytomel you will want to pay particular attention to your free T3, total T3, reverse T3, and sex hormone-binding globulin.

These lab tests are more important than assessing the TSH because they give you information as to how your body is processing and utilizing free thyroid hormone. 

Another helpful measure is to evaluate your free T3:reverse T3 ratio which can give you an idea of how much competition there is at the cellular level. 

The higher your reverse T3 is the more competition exists between thyroid receptors for T3 and rT3. 

You can also evaluate your TSH but you should remain cautious when doing so because T3 is about 3x more potent (6) than T4 at lowering the TSH. 

Instead, use the other measures and lab tests listed above to get an idea of how well your body is utilizing serum levels of T3. 

If your body is utilizing the T3 and Cytomel correctly then your Free T3 should be increasing, your Reverse T3 should be decreasing and your SHBG should be increasing. 

#2. Your Basal Body Temperature

Basal body temperature can be used as a surrogate marker of thyroid function, but like the other areas here should NOT be used in isolation.

Cytomel and other forms of T3 have been shown to increase Basal body temperatures (usually in supraphysiologic doses (7)).

​And this makes sense when you think about how thyroid hormone works:

Thyroid hormone helps with cellular energy production which helps generate heat (8). 

Low thyroid hormone = low energy production = low body temperature. 

Now, while that’s true there are also many other things that can cause low body temperature including several medications. 

The more medications you are on (Like beta blockers) the less accurate your basal body temperature becomes. 

Despite this, I still recommend following the body temperature while on T3-containing medications. 

#3. Your Resting Heart rate

Cytomel and T3 thyroid hormones have a direct effect on the heart and cardiac tissue.

Cytomel causes an increase in the force of contraction and an increase in the heart rate (9).

The main difference between the heart and other tissues when it comes to thyroid hormone is the effects at the cellular level:

T3 has both nuclear and extranuclear effects (10) on the heart. And that’s important because the extranuclear effects cause an increase in heart rate via calcium channels. 

This is important because other cells in your body have to take in thyroid hormone via the nucleus and process changes through genetic transcription (11). 

That’s a bunch of mumbo-jumbo to say that the effects of thyroid hormone on the heart are more rapid than the effects of thyroid hormone on other tissues.

This means your heart can be more sensitive to the medication, even though your other cells still need the hormone.

However, when titrating your dose it’s ALWAYS important to monitor how it affects cardiac tissue because it is very sensitive.

#4. Your Thyroid Symptoms

​The main reason you are probably on thyroid medication is to reduce the symptoms of hypothyroidism you are experiencing!

So it makes sense that while you increase your dose of Cytomel or T3 your hypothyroid symptoms should decrease, right?

Well, that is true for the most part but it’s important to remember that not all of your symptoms are necessarily related to or caused by thyroid dysfunction. 

For instance, your fatigue may be caused by a combination of hypothyroidism plus adrenal-related issues plus nutrient deficiencies. 

In this case, it doesn’t make sense to titrate up your Cytomel until your fatigue disappears because you won’t be addressing the underlying cause.

While it is helpful to monitor your symptoms as you increase your dose, don’t rely completely on your symptoms alone as this may lead to overdosing (12). 

Cytomel Reviews & Case Studies

Remember that Cytomel can be used in combination with other medications for a more powerful medication combo.

I will frequently use Cytomel in combination with NDT.

And even though many providers aren’t comfortable with this combination, some endocrinologists and PCPs may be more likely to add Cytomel to your Levothyroxine dosage.

Sometimes even adding as little as 10-20mcg per day to your dose may improve your symptoms dramatically.

To see some case studies on T3 and how it can help with weight loss and improve low thyroid symptoms please see this post. ​

Do you Need to Switch Thyroid Medications?

​While there is no perfect thyroid medication that everyone HAS to be on, Cytomel certainly has its place in many patients. 

In general, the more complex a patient is the better they tend to do on Cytomel.


Because chronic infection, chronic pain, chronic illness, insulin resistance, and leptin resistance all put a brake on your thyroid conversion process and favor the production of Reverse T3.

When you take T3-only medication like Cytomel, you are not providing your body with the substrate to produce reverse T3 so these levels often decrease dramatically. ​

I generally recommend Cytomel who patients who fall into these categories:

  • Patients with very high reverse T3 levels (often > 15 or even higher)
  • Patients with Insulin resistance, pre-diabetes, or diabetes
  • Patients with Leptin resistance (Serum leptin levels > 10)
  • Patients with a personal history of Bipolar disorder, severe medication-resistant depression, or a family history of both
  • Patients with fibromyalgia, chronic fatigue syndrome, or chronic pain syndromes
  • Patients who have very complex medical histories and have been sick for decades
  • Patients who have failed NDT or T4-only medications

Remember that these are just recommendations and you shouldn’t live or die by these guidelines. 

At the end of the day, you are a unique individual and you should be treated as such. 


​Cytomel is the strongest of the thyroid medications because it contains T3 instead of T4 like most other medications

It can be used in conjunction with other thyroid medications or by itself and it can also be compounded in various forms to delay its release into the bloodstream. 

Side effects from Cytomel are generally caused by either a hypersensitivity reaction to the binders and fillers inside of the medication or due to the dosage being too high. 

If you experience side effects due to the binders or fillers, you may be able to change medications to SR T3 to get around these side effects. 

If you experience side effects due to your dose, then you may need to address underlying nutrient deficiencies before raising your dose. 

If these symptoms still persist then it may be necessary to switch to NDT or T4 medications. 

Now I want to hear from you:

Have you taken or are you currently taking Cytomel?

Have you experienced any adverse side effects?

Is it helping you feel better? Is it helping you to lose weight?

Why or why not?

Leave your comments or questions below! 

Scientific References













cytomel side effects explained pinterest image.

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About Dr. Westin Childs

Hey! I'm Westin Childs D.O. (former Osteopathic Physician). I don't practice medicine anymore and instead specialize in helping people like YOU who have thyroid problems, hormone imbalances, and weight loss resistance. I love to write and share what I've learned over the years. I also happen to formulate the best supplements on the market (well, at least in my opinion!) and I'm proud to say that over 80,000+ people have used them over the last 7 years. You can read more about my own personal health journey and why I am so passionate about what I do.

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