Is the Ketogenic Diet Safe if you have Thyroid Problems?

If you have thyroid problems and you are considering the ketogenic diet then this it the article for you. 

In it, we are going to explore why the ketogenic diet may potentially be harmful to your thyroid, how it may potentially help your overall situation, and how to determine if it's right for you. 

Highlights from the article:

  • The ketogenic diet may help with weight loss but it may not be safe for your thyroid. 
  • Whether or not the ketogenic diet will negatively impact your thyroid depends on a number of factors. 
  • Weight loss may help improve your thyroid through weight loss and improving leptin sensitivity. 
  • It may damage your thyroid through suppressing your free thyroid hormone levels and increasing your TSH. 
  • Be cautious if you decide to use this diet and check your thyroid lab tests regularly or about every 6 weeks.


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 this is coming from someone who has done keto himself and has put a great many patients on this diet early on in my career. 

But it became apparent to me (back in 2013-2014) 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. 

ketogenic diet in the news

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 are 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 their weight loss. 

I am primarily going to focus on this 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 2012ish. 

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 or reacted 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 even more people had either no reaction or a negative reaction. 

My weight loss therapies would be considered somewhat aggressive, so when a patients 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 (she wasn't happy about this). 

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

From these experiences, I adopted a better approach which is to individualize each person's dietary needs and align them with various other factors that they may be dealing with. 

But, since most of you don't have a doctor willing to do that for you, it's worth exploring the potential benefits and risks that this diet affords. 

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 these may positively impact your thyroid. 

#1. Weight Loss

Yes, losing weight (if done correctly) can have a positive impact on your thyroid. 

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), but this doesn't explain the whole picture. 

What is the "standard" way to lose weight?

It's calorie restriction.

So, all of the studies that we have which show this trend occur as a result of 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? 

If done correctly, and if it is not associated with calorie restriction, then the ketogenic diet can help with weight loss which may positively impact 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. 

But, this is true only if your weight loss is not dramatic, associated with a decline in calories, and if done over a reasonable period of time. 

Dramatic drops in your weight may trigger these negative changes (discussed more below). 

#2. Leptin Sensitivity

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

Weight gain itself is a potential cause of leptin resistance. 

The more weight that you have on your body 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/free T4 levels (3). 

If you can do anything in your body to sensitize your brain to leptin (assuming you have leptin resistance) then you will necessarily improve thyroid function indirectly. 

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

This may be complicated by the fact that some studies show that the ketogenic diet may actually increase leptin levels (4). 

This may sound ideal, and it should be, but only if you are a 5-10 pounds overweight. 

Increasing leptin levels is the last thing you want to happen if you are suffering from moderate to severe leptin resistance because high leptin levels are what caused the resistance in the first place. 

Your underlying leptin status may be part of the reason why some people respond well to the ketogenic diet and why others do not. 

The Potential Harm for your Thyroid

The ketogenic diet isn't all benefits, however, and I tend to think of this diet as potentially causing more harm than good for most thyroid patients. 

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

Those people with hypothyroidism know how difficult it can be to get their doctors on board with newer treatments which include medications that contain T3. 

So why would you want to risk further damaging your thyroid with a 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. 

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

#1. Suppressed 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 in some studies (5). 

There simply aren't many studies which show the connection between thyroid function and the ketogenic diet, but what few studies we have, do show a potential negative outcome. 

This research, while done in children, mimics what I've seen in my own personal practice. 

Even in some people who 'feel well' their thyroid function seems to decline as evidenced by a drop in free t3/total T3 and a rise in their TSH

This is a classic presentation for hypothyroidism and probably represents early damage to the hypothalamic-pituitary-thyroid axis. 

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. 

It appears that there are some people who are at increased risk of thyroid damage when doing the ketogenic diet. 

Whether or not your thyroid lab tests will be suppressed likely depends on a number of factors including:

  • Are you eating 'healthy' fats?
  • Are you restricting your daily caloric needs?
  • How long have you been in ketosis?
  • Were you adequately treated with thyroid hormone before you started?
  • Are you also over-exercising, over-stressed or over-worked?
  • Do you have a strong family history of thyroid disease?

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 the ketogenic diet. 

This isn't perfect, but it is a good way to assess whether or not you should even consider the diet in the first place. 

#2. Inability for your thyroid to respond if you are on thyroid medications

Another potential issue for thyroid patients is the fact that they are taking thyroid medications

Thyroid medications help to supplement thyroid hormone in their body to replace whatever their own body can't produce naturally. 

The only problem with this is that the more medication you take the more you suppress your own native thyroid hormone production from your thyroid gland. 

This becomes an issue when you undergo things like the ketogenic diet which may influence how much thyroid hormone your body needs (or the demand on your thyroid gland). 

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 new demands. 

This is only really a problem for people who have doctors who aren't willing to work with them as they undergo weight loss, new therapies, or new diets because this problem doesn't necessarily have to prohibit you from these therapies. 

So, if you find that the ketogenic diet puts an increased demand on your thyroid gland, you may need to either increase the dose that you are taking. 

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 dose. 

#3. Further Hormone Imbalances

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

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

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

What you really want to avoid is further stress on your body which may cause cortisol-related issues. 

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

And if this stressor tips the balance of positive and negative stress towards the negative side of the spectrum, then it may cause further issues for 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 who tries the ketogenic diet, but it's something worth considering. 

Like your thyroid, you can easily test for these hormones as you undergo the diet. 

Should you Use it? 

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 other people are getting. 


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 every 6 weeks or so. 

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 body is NOT tolerating the diet. 

You can get your thyroid lab tests at baseline BEFORE you start the diet to compare your new results to. 

thyroid metabolism reset poster for side bar

Beware, though, if you make changes to your thyroid medication during this time period then this may invalidate the effectiveness of testing your thyroid lab tests. 

If you decide to use it you should very closely monitor both how you are feeling and how

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 which 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. 

My personal recommendation would be to use this diet temporarily 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. 

Once you have done this you should be able to transition to a regular diet without any issue. 

You just better hope you don't damage your thyroid along the way, otherwise, you may gain that weight back due to metabolic damage! 

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. 

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 which 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 a quality one. 

In addition, it's also just as likely that these people who have low thyroid function have other genes which improve thyroid sensitivity at the cellular level which means that they simply need less thyroid hormone than other people. 

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. 

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. 


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! 

References (Click to Expand)

ketogenic diet thyroid
Dr. Westin Childs

Dr. Westin Childs is a Doctor of Osteopathic Medicine. He provides well-researched actionable information about hormone-related disorders and formulates supplements to treat these disorders.He is trained in Internal Medicine, Functional Medicine, and Integrative Medicine. His focus is on managing thyroid disorders, weight loss resistance, and other sex hormone imbalances.You can read more about his own personal journey here.

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