Is the Ketogenic Diet Safe if you have Thyroid Problems?

Is the Ketogenic Diet Safe if you have Thyroid Problems?

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Thinking about the keto diet with a thyroid problem? 

You may want to think twice. 

While there are some benefits to using the ketogenic diet for weight loss, it may come with some unwanted baggage for your thyroid. 

In this article, we will explore why the ketogenic diet may potentially be harmful to your thyroid, when it makes sense to try the ketogenic diet, and how to determine if it’s right for you. 

Today you will learn:

  • Why the ketogenic diet may help with weight loss but why it may not be safe for your thyroid. 
  • How going keto may negatively impact your thyroid.
  • Why weight loss is beneficial for your thyroid and how it impacts insulin and leptin levels.
  • Why the ketogenic diet may suppress free thyroid hormone levels and what that means for your labs and thyroid medication dose.
  • Why you need to check your thyroid lab tests before using this diet. 
  • And much more…

The Ketogenic Diet and your Thyroid

I’m not going to spend time explaining exactly how the keto diet works (there are plenty of places where you can read about that right now), instead I want to focus on its impact on thyroid function and whether or not it is safe for thyroid patients. 

As many of you probably know, I’m not a huge fan of the ketogenic diet. 

And I’m not just saying that without experience. 

I have personally used the ketogenic diet and have recommended it to many patients. 

I even have some weight loss case studies on my website outlining patients who have used it successfully. 

Despite using it with some success, it became apparent to me (back in 2013-2-14) that this diet is certainly not for everyone. 

While it potentially can be used as a great tool for certain people, I don’t think it should be universally recommended, especially for thyroid patients. 

Because this diet has hit the mainstream, it’s now common for all kinds of people to jump into this diet head first. 

This is both good and bad. 

Good in the sense that many people are losing weight, and bad in the sense that there will be a large number of people with newly diagnosed thyroid issues for the foreseeable future

When I talk about the keto diet and its impact on thyroid function, I want to talk about 2 separate groups of people. 

The first group is those who do NOT have any thyroid issues but who develop thyroid problems or thyroid lab abnormalities as a result of going on the diet. 

The second are those people who have existing thyroid disease (Hashimoto’s, those without a thyroid, those taking thyroid medication, etc.) who are considering going on the diet to see if it will help with weight loss. 

For the purposes of this article, I want to focus on the second group. 

And my recommendation to these people is to proceed with caution

Let’s talk about why.


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My Experience with the Ketogenic Diet

I attribute much of my own personal healing to changing up my diet which included being in ketosis for several months back in 2012. 

While changing my diet certainly helped improve many aspects of my health, it was certainly not perfect and I ultimately had to alter the type of diet that I was using several times in order to feel completely better. 

But because I noticed that it was so effective, I began to recommend it to certain patients. 

Because most of my patients had thyroid disease, I was able to see how they responded to this diet. 

What I found was a mixed bag. 

Some people responded very well, lost weight, had increased energy, and experienced the type of outcome that most of you are looking for. 

But a much larger percentage of people had either no reaction or a negative reaction. 

My weight loss therapies and recommendations would be considered somewhat aggressive, so when a patient’s weight is staying the same it’s never a good sign. 

I even tested the diet on my wife (I test most therapies on my family members) and she ultimately gained around 13 pounds. 

As you can imagine, she wasn’t very happy about this.

Relevant to this discussion is that at the time she went keto she suffered from high reverse T3 and thyroid resistance

You’ll find out why this is important and why understanding your thyroid function before you go keto is a good idea. 

These experiences taught me a few important things:

#1. That each person with thyroid disease requires a different and unique diet. 

#2. That it’s difficult (impossible) to make broad diet recommendations for all thyroid patients. 

And #3. Even though some diets can be helpful for many, they also have the potential to cause harm for others.

The Potential Benefits For Your Thyroid

Is the ketogenic diet all bad?

The answer is no. 

In fact, it can be a great asset and tool for many people (including some with thyroid disease). 

My goal here is not to scare you away from this diet altogether, but it is to teach you to have a healthy respect for therapies and how they may potentially impact your thyroid in a negative way. 

We’ll talk more about the negatives below, but for now, let’s focus on the positives and how the ketogenic diet may help improve your thyroid. 

#1. Keto can be great for weight loss

Believe it or not, losing weight (the right way) can actually help your thyroid to function more optimally. 

Several studies have shown that weight loss is usually associated with a decline in free T3, total T3, and an increase in reverse T3 (1). 

You might look at this and think, “why would I want to LOWER my thyroid if I’m already hypothyroid?! Wouldn’t that make me feel worse?”. 

You would think so but that isn’t the whole picture. 

What is the “standard” advice given to thyroid patients that want to lose weight?

The advice you will be given by your doctor or nutritionist is to eat less and exercise more. 

In other words, calorie restriction. 

What does this mean?

It means that the studies which show how weight loss impacts thyroid function occur as a result of weight loss from calorie-restricted diets. 

If you want to lose weight long-term, then this is absolutely NOT the way to do it because these types of diets WILL damage your metabolism and your thyroid. 

But what about the ketogenic diet? Is there something different in how keto helps you lose weight compared to calorie-restricted diets?

The answer is yes. 

If the keto diet is done correctly, and if it is not associated with significant or sustained calorie restriction, then it can help with weight loss which may then improve your thyroid. 

In this setting, it doesn’t necessarily have to be associated with a decline in free T3, total T3, or an increase in reverse T3. 

In fact, weight loss can actually promote normal thyroid function (2) as hormones such as leptin and insulin decrease. 

By virtue of carbohydrate reduction, keto tends to have a profound impact on insulin sensitivity. 

#2. Keto may help improve leptin sensitivity and leptin resistance

The second way that the ketogenic diet may positively impact your thyroid is through its influence on the hormone leptin. 

Leptin is one of the most important hormones that your body uses to help regulate your weight and your metabolism. 

As you gain weight and are unable to lose it, leptin levels will increase and you may develop what is known as leptin resistance. 

The more weight that you have on your body and the longer that it’s been there, the more likely you are to be leptin resistant. 

And leptin resistance negatively impacts thyroid function through the hypothalamus by reducing your metabolism and by reducing free T3 and free T4 levels (3). 

Any therapy which helps your body become more sensitive to leptin will help you lose weight and help improve your thyroid indirectly. 

And because the ketogenic diet can help with weight loss it may also help sensitize your brain to leptin. 

Some studies show that the ketogenic diet may actually increase leptin levels (4). 

This may seem confusing based on what we’ve discussed so allow me to explain. 

When you have mild leptin resistance (or just a few pounds to lose) an increase in leptin can paradoxically help you lose weight. 

It’s not until you have moderate to severe leptin resistance (or 50+ pounds to lose) that increasing leptin for weight loss becomes a problem. 

This is why you will see bodybuilders often talk about ways to increase leptin. 

Increasing leptin is beneficial for fat loss when you are close to your target weight. 

But the farther you get from that target weight the more you want to focus on lowering leptin (not increasing it). 

The Potential Harm To Your Thyroid

While there are certainly benefits to going keto, we have to talk about the downsides as well.

Based on my experience and reading of the research, I tend to think of this diet as potentially causing more harm than good for most thyroid patients. 

Note that I did not say ALL thyroid patients, though!

There are still some patients (perhaps you reading this) that can benefit from it. 

The reason I feel this way is that managing and balancing your thyroid is already so tenuous and difficult, to begin with. 

If you have hypothyroidism then you already know how difficult it can be to get your doctor on board with newer treatments, the use of supplements, and thyroid medications that contain T3. 

So why would you want to risk further damaging your thyroid with the keto diet when the consequence may be very difficult to deal with?

I’m not saying that it’s impossible to repair your thyroid after you damage it, but it certainly takes a long time and you better be sure that whatever therapy you are doing is worth this potential risk. 

For what it’s worth, I find that most of the time damage done to the thyroid from diets or therapies can be fixed with the right treatments or right thyroid medication. 

So the risk of long-term harm is usually minimal. 

And most people can simply stop the offending therapy (in this case diet), to normalize their thyroid function again. 

With this in mind, let’s talk about some documented ways that the keto diet can impair your thyroid. 

#1. Going keto may suppress your thyroid hormones

The first reason you want to be careful with the ketogenic diet is that it has been shown to suppress free thyroid hormone levels (5). 

This research, while done in children, mimics what I’ve seen in the real world.

There are some thyroid patients who feel well while using the keto diet but upon testing their thyroid, notice that their thyroid function declined from their baseline. 

These patients often see a decline in free T3 and total T3 and a slight rise in their TSH.  

This is a classic presentation of hypothyroidism and probably represents early damage to the hypothalamic-pituitary-thyroid axis prompted by the effects of the keto diet. 

If you start to see this sort of change in your thyroid lab tests while you are using the ketogenic diet then it is probably a good idea to stop as soon as possible. 

But, as I said previously, just because it happens to some people doesn’t mean it will happen to everyone. 

For whatever reason, there are certain thyroid patients who are at increased risk of thyroid damage when doing the ketogenic diet. 

We don’t know exactly why this happens but the following factors are likely playing a role:

  • The type and quality of fat you are consuming to get into ketosis
  • Whether or not you are restricting your calories and to what degree
  • The duration of time you’ve been on the ketogenic diet
  • Your thyroid status prior to going keto (was it optimized before starting or were you underdosed or mismanaged?)
  • Whether or not you were over-exercising, over-stressed, or over-worked while in ketosis
  • A strong family history of thyroid disease (your genetic history)

If you are eating unhealthy fats, if you are restricting your calories, if you’ve been in ketosis for a long time (6+ months), if you weren’t adequately treated with thyroid medication before you started, if you are also over-stressed/over-worked, and if you have a strong family history of thyroid disease, then you are probably more likely to experience a decline in thyroid function with this type of diet. 

This isn’t a perfect way to assess your risk of a negative outcome but it is a good way to assess whether or not you should even consider the diet in the first place. 

It stands to reason that the more risk factors you have the more likely you are to see thyroid problems when going keto. 

#2. Going keto may result in the inability of your thyroid to respond to thyroid medications

Another complicating factor when considering keto is the use of thyroid medication

Thyroid medications, such as levothyroxine, are frequently used to help boost thyroid hormone levels in cases of hypothyroidism or low thyroid function. 

These medications are so common that they are frequently at the top of the list of most prescribed medications in the United States. 

While thyroid medications can help you feel better and improve your symptoms, they come at the cost of your body’s ability to produce its own thyroid hormone. 

In other words, thyroid medication shuts down your thyroid gland in a dose-dependent manner. 

This may become an issue when you use the ketogenic diet because it can influence how much thyroid hormone your body needs. 

Because your gland is being suppressed by the medication you are taking, you aren’t able to fully respond to these new demands. 

This means you MUST address your thyroid medication (either up or down) based on these changes. 

For most thyroid patients, this may not be a big deal. 

But if you are someone that is struggling to get your doctor on board with new therapies or new diets (such as the keto diet), changes to your thyroid function can be used as ammunition to try to get you to stop. 

And, yes, this does happen. 

I’ve seen many thyroid patients undergo therapies that make them symptomatically feel better only to have their doctor recommend they stop because their doctor isn’t familiar with them. 

So, if you find that the ketogenic diet puts increased demand on your thyroid gland, you may need to alter your dose of thyroid medication to compensate. 

On the other hand, it’s also possible that the ketogenic diet may improve your thyroid function which may necessitate a reduction in your thyroid medication dose. 

#3. Going keto may cause other hormone imbalances in thyroid patients

Lastly, it’s also possible that using the ketogenic diet may negatively impact other hormones in your body which may have an indirect impact on your thyroid. 

The hormones that I am referring to here include progesterone, cortisol, and estrogen. 

All three of these hormones can be positively (or negatively) impacted by the ketogenic diet. 

Of the three listed, cortisol may be the most important. 

Cortisol is considered a stress hormone and is released during times of stress. 

From the perspective of your body, pretty much any change counts as stress. 

Changing your diet, even if it’s causing positive changes overall, is still considered a stressor on the body. 

And if this stress tips the balance towards the negative side of the spectrum, then it may cause further issues to your overall health and your thyroid. 

It is well known that there is a connection between cortisol levels and your TSH (6) such that problems in one will drag down the other. 

Again, this isn’t going to necessarily be a problem for everyone that tries the ketogenic diet, but it’s something worth considering. 

Should You Go Keto?

Your decision to use the ketogenic diet should be between you and your doctor (if you have one willing to work with you) and it should not be dependent upon the results that you see from other people. 


Each person is genetically unique which means that how you respond to any given therapy is different from the next person. 

My own personal experience suggests that the ketogenic diet is probably not ideal for the majority of thyroid patients, but somewhere between 20-25% may experience some benefit while using it. 

Determining if you fit into that 25% can be done through careful testing and monitoring of your symptoms. 

If you decide to use the ketogenic diet then you should be very cautious and closely monitor your thyroid lab tests on a regular schedule. 

Checking your TSH, free T3, free T4, reverse T3, and total T3 can and should be done 8 weeks after starting the diet and at least quarterly thereafter. 

If you find that your TSH rises, your free T3/free T4/total T3 lower, or your reverse T3 rises, then these may be early signs that your thyroid is NOT tolerating the diet. 

Before you go keto, make sure to grab a baseline set of thyroid lab tests that you can compare future results to. 

Be aware that making changes to your thyroid medication during this period of time may invalidate the accuracy of your thyroid lab tests.

In addition to checking your thyroid lab tests, if you go keto you will also want to pay close attention to how you are feeling. 

If you see an abrupt increase in your thyroid symptoms then that may be an early warning sign your thyroid is not tolerating the diet. 

It’s probably also not a good idea to stay on the keto diet long-term, even if it is working for you. 

It’s important to understand that there are no long-term studies that prove that this diet is safe or effective (7) for your overall health if done for years in a row. 

In fact, many of the proponents of the ketogenic diet (those who taught me about this diet) only use it temporarily on themselves!

Going in and out of ketosis may be superior rather than staying in ketosis without any breaks. 

It may also be better to use the ketogenic diet temporarily to help with something like weight loss and then transition to other diets which are considered safer for your thyroid. 

This can actually be done safely because the entire goal of using the ketogenic diet is to reset insulin/leptin levels and help with weight loss (at least that’s why most people use it). 

Ketogenic Diet After Thyroidectomy

Does this information apply to you if you don’t have a thyroid or if your thyroid has been destroyed with radioactive iodine?

The short answer is yes. 

All of this information is still relevant to you but you should also proceed with slightly more caution than those with a functioning thyroid. 


Because, unlike them, you are 100% reliant upon thyroid medication to support the needs of thyroid function in your body. 

And people without a thyroid are generally undertreated as evidenced by the fact that most people gain weight after their thyroidectomy and suffer from the symptoms of hypothyroidism

I say proceed with caution because if you elect to use the keto diet then you must be prepared to make changes to your thyroid medication dose. 

Again, it’s not really a reason to avoid it 100%, but you will probably need to have your doctor on board with you to help regularly check and adjust your thyroid medication as needed. 

The Low T3 Longevity Argument

Lastly, I want to spend some time on the low t3 longevity argument. 

It’s been suggested that the ketogenic diet is safe to use even if it does lower your T3 levels (or thyroid function) because some studies have shown that people who have lower thyroid function tend to live longer (8). 

While it may be true that a few studies have shown this, it doesn’t in any way prove that low thyroid function leads to a long life. 

In fact, even if it did lead to a long life, we have a number of studies that show that low thyroid function (especially low T3) is also associated with weight gain, fatigue, depression, and many other negative symptoms. 

So even if having low T3 did lead to a longer lifespan, the life that you would be living would not necessarily be of high quality. 

One potential explanation for low T3 and longevity may have to do with thyroid sensitivity. 

It may be that certain people have genes that improve thyroid sensitivity at the cellular level which means they need less thyroid hormone than the average person. 

In other words, their labs look like they have less T3 when in reality their cells are functioning as if the level was higher. 

That or any number of other explanations could potentially explain why we see that low thyroid hormone in the serum may be associated with increased longevity. 

If you are a thyroid patient already, then you can always reduce your dose of thyroid hormone temporarily to experience how you might feel with low thyroid hormone (although this wouldn’t be recommended for obvious reasons!). 

If you’ve ever done that before please reply back here with your experience! I’m sure it wasn’t a positive one. 

The bottom line?

Don’t necessarily jump in on the ketogenic diet just because you feel that it will improve your lifespan. 

Final Thoughts

The ketogenic diet isn’t all benefits without any consequences. 

If you are thinking about using this diet AND you have thyroid disease then please be cautious. 

It’s possible, and probable, that undergoing this diet may negatively impact your thyroid in a number of ways. 

If, however, you’ve tried every other therapy and no matter what you do you can’t seem to find any relief, then a trial of this diet may be in order. 

If you elect to go down this path then make sure that your doctor is on board and willing to test your thyroid lab tests regularly and adjust your medication as necessary. 

Don’t just jump into the hype of the ketogenic diet, however, because you don’t want to put yourself in a situation that ultimately makes your thyroid function worse. 

Now I want to hear from you:

Have you tried the ketogenic diet?

Did it work for you? 

Did it help with weight loss?

Did you notice any damage or changes to your thyroid?

Why or why not?

Leave your questions or comments below! 









why keto should be avoided if you have a thyroid problem

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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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