Ketogenic Diet and Hypothyroidism

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Keto diet has become one of the most popular diet trends in the world lately. An increasing number of people adhere to ketogenic diet and report amazing weight loss, better blood sugar control, and improved overall health.

Despite its popularity, the safety of keto diet for hypothyroid patients is not frequently discussed. Is keto diet safe for hypothyroid patients?

Does it have a positive influence on thyroid hormones? Scroll down to find out!

What is a Keto diet?

Ketogenic, or keto, diet is a high-fat, moderate protein, and low-carb dietary pattern which is usually recommended for persons with insulin resistance and diabetes but is used for many other purposes today as well. Similar to other low-carb diets such as Atkins, ketogenic diet drastically reduces consumption of carbohydrates and replaces them with healthy fats to put the body into the process of ketosis.

Ketosis is a natural metabolic state wherein fat fuels the body with energy. This metabolic state allows the body to burn fat for energy more effectively thus contributing to weight loss. At the same time, ketosis also involves the conversion of fat into ketones in the liver to deliver more energy to the brain.

Although it is incredibly popular today, the ketogenic diet is not the latest trend or fad. The diet was created back in the 1920s for patients with epilepsy by scientists who worked at Johns Hopkins Medical Center[i].

The core of ketogenic diet is to significantly reduce the intake of sugars and starches because these foods are broken down into glucose and insulin in the blood once we eat them. When insulin and glucose levels become excessive, extra calories are stored as body fat thus leading to weight gain. It is needless to mention this can only cause further damage in persons with diabetes.

Today, keto diet has become a major trend, and its advocates praise the incredible health potential of the diet. Some health benefits linked to keto diet include:

  • Weight loss
  • Reduced risk of type 2 diabetes
  • Lower risk of heart disease
  • Cancer prevention
  • Management of brain diseases and neurological disorders
  • Longer life

Keto and hypothyroidism

Keto diet is one of the most popular diets today mostly because social media influencers often credit it for their slim figure. However, just because something is popular, it doesn’t mean it is effective or safe for everyone.

If you have hypothyroidism and are considering keto diet, you should read this post first prior to making a final decision. Why? It turns out keto diet is not, actually, the best option for hypothyroid men and women. Before you start thinking it’s a baseless claim, keep in mind that science has confirmed it.

Fontana L. et al. carried out an interesting study that evaluated the influence of caloric restriction on thyroid hormones in 28 men and women. Findings revealed that caloric restriction lowers the concentration of T3 hormone[ii]. The primary reason why the lower calorie consumption decreases T3 is to improve the chances of survival when our ancestors, back in time, were dealing with food shortage. As a result, metabolism slows down, and the body burns fewer calories.

That being said, low levels of the T3 hormone are not desirable for hypothyroid patients. Since keto diet is associated with calorie restriction, then it’s easy to understand this dietary pattern could exhibit a negative impact on thyroid hormones.

Keto diet was specifically created to mimic fasting[iii] or starvation from the metabolic perspective. Why does this matter? Well, a growing body of evidence confirms that starvation limits production of hormones T3 and T4[iv]. As a result, keto diet disrupts the metabolism and further impairs production of hormones. It is needless to mention that hypothyroidism is indicated by insufficient production and concentration of thyroid hormones.

Therefore, adhering to this diet puts the body into starvation/fasting mode (from a metabolic point of view) which is not good news for T3 and T4 levels produced by the butterfly-shaped gland.

Decreased levels of T3 hormone allow for a deeper state of ketosis, and they preserve muscle mass. Of course, this applies to healthy individuals. In hypothyroid patients, hormone levels are out of balance, and it may not work that way.

At this point, evidence about keto diet and its influence on thyroid hormones is limited. More research is necessary to explore this dietary pattern and its impact on production of thyroid hormones, function of butterfly-shaped gland and safety of use among hypothyroid patients.

Although limited, the evidence is not nonexistent. In these cases, it is always best to be cautious before rushing to make drastic changes in your diet.

Low-carb diet – low thyroid hormones

One of the most recent studies on the subject of ketogenic diet and thyroid hormones was published in April 2017, and it had interesting findings. Kose E. et al. discovered that keto diet has the potential to cause thyroid malfunction which may necessitate levothyroxine treatment[v]. As you already know, levothyroxine is one of the most commonly used medications for treatment of hypothyroidism.

Bisschop P.H. et al. conducted a separate study whose main objective was to evaluate the impact of higher or lower carbohydrate consumption on thyroid hormones. For the purpose of the research, scientists measured resting energy expenditure, thyroid hormone levels, and other parameters in six men. Findings, published in the Clinical Endocrinology journal, revealed that high intake of carbs did not influence thyroid hormones. On the flip side, low carbohydrate consumption decreased levels of the T3 hormone[vi].

In other words, current evidence reveals that high intake of carbohydrates does not exhibit negative effects on the thyroid gland, but low intake of these macronutrients could disrupt production of thyroid hormones.

Keto diet and Hashimoto’s thyroiditis

Hashimoto’s thyroiditis is an autoimmune condition and the most common cause of hypothyroidism. In autoimmune diseases, the body’s immune system starts attacking healthy cells, tissues, and organs. While the anti-inflammatory potential of keto diet may be a good reason to consider adhering to this diet and manage symptoms of Hashimoto’s, you should think twice about it.

The biggest problem with keto if you have this autoimmune condition is that areas of the brain which regulate the function HPA (hypothalamic-pituitary-adrenal) axis needs glucose to work properly. As seen above, glucose is necessary for energy or fuel.

In addition, TSH is partially comprised of glucose molecules. It’s also important to mention that Spaulding S.W. et al. showed severe carb restriction decreases T3 levels while increasing reverse T3 (rT3) concentration[vii]. What does this mean? Basically, elevated rT3 expression contributes to and aggravates symptoms of hypothyroidism in patients with Hashimoto’s.

If you have Hashimoto’s thyroiditis and want to try the keto diet, you can think about modifying it a little bit. Try not to cut carbs in such a severe manner. Consult your doctor or ask a nutritionist for help.

Low carb without keto

Let’s be honest, and low-carb diets are nothing new. For decades men and women have been trying to slim down by lowering consumption of carbs. Keto is different because the goal is to start or promote ketosis. Not all low-carb diets are focused on ketosis.

A person can decrease intake of carbs without following a strict meal plan or dramatically reducing consumption of these macronutrients. So, it’s natural to wonder whether low carb diet, without keto, would harm your thyroid hormones especially if you are a hypothyroid individual. It turns out, and this meal plan could be safe.

Nuttall F.Q. et al. discovered that slightly reducing intake of carbs (without starting ketosis) is highly unlikely to exhibit a negative impact on thyroid hormone levels[viii]. On the other hand, Hendler R. et al. found that 1% carb diet was linked to a greater reduction in T3 hormone levels compared to 55% carb diet group[ix].

These findings could indicate that the greater reduction of carbs intake, the bigger the influence on T3 hormone production.

If you want to lower carbs intake and lose weight or start a healthier lifestyle, strive not to make some drastic changes. Even small reduction can go a long way. This is the problem with the keto diet, it is too restrictive, and when the body is deprived of a certain nutrient, it experiences various reactions some of them being disrupted T3 production.

How to follow Keto if I am hypothyroid

As seen throughout this post, ketosis may have a major impact on your thyroid hormones. But, if you’re curious and want to try it to see how it will work for you, then there are some things to bear in mind. Some people are curious about keto diet due to its potential to regulate blood sugar, promote weight loss, and alleviate inflammation all of which are important concerns for hypothyroid patients.

The first thing to do is to consult your doctor and see whether they’d recommend keto or what they would suggest instead. For many patients following keto on a regular basis may be counterproductive due to effects discussed in this article. However, following keto in cycles is a practical solution for some hypothyroid patients.

Foods to eat and avoid for hypothyroidism

Nowadays we are led to believe that in order to slim down, address a specific health problem, and achieve body goals, we need to follow a specific diet plan. New diets emerge all the time thanks to social media. However, you don’t have to follow some particular diet in order to feel better and manage hypothyroidism.

It all comes down to modifying your eating pattern and make it more balanced. Of course, it’s always useful to get input from your doctor to see whether you’re on the right path.

Persons with hypothyroidism should enrich their diet with eggs, meats, vegetables, fish, fruits, gluten-free grains, and seeds, dairy, and drink plenty of water. That being said, you may want to avoid heavily processed foods because they have little to no nutritional value, but carry a high risk of hormonal imbalance.

At the same time, hypothyroid patients are often advised to lower intake of foods that contain gluten, soy foods, cruciferous vegetables, alcohol, and certain fruits.


Millions of people around the world adhere to Keto diet and praise it for their weight loss, blood sugar control, and what not. Since hypothyroidism is associated with weight gain, many patients are tempted to start with this diet as well.

While the simple reduction in carbohydrate intake may not alter thyroid hormone production, severe carb restriction and ketosis can contribute to thyroid malfunction. If you’re hypothyroid, the best thing to do is to consult your doctor before making drastic changes on your own.

Instead of dramatically restricting carbs from the diet, you can just lower the consumption so that your body still gets what it needs from them.


[i] The Ketogenic Diet Center, Johns Hopkins Medicine

[ii] Fontana L, Klein S, Holloszy JO, Premachandra BN. Effect of long-term calorie restriction with adequate protein and micronutrients on thyroid hormones. Journal of Clinical Endocrinology and Metabolism 2006 Aug;91(8):3232-5. Doi: 10.1210/jc.2006-0328

[iii] Wheless JW. History of the ketogenic diet. Epilepsia 2008 Nov;49 Suppl 8:3-5. Doi: 10.1111/j.1528-1167.2008.01821.x

[iv] Douyon L, Schteingart DE. Effect of obesity and starvation on thyroid hormone, growth hormone, and cortisol secretion. Endocrinology and Metabolism Clinics of North America 2002 Mar;31(1):173-89

[v] Kose E, Guzel O, Demir K, Arslan N. Changes of thyroid hormonal status in patients receiving ketogenic diet due to intractable epilepsy. Journal of Pediatric Endocrinology and Metabolism 2017 Apr 1;30(4):411-6. Doi: 10.1515/jpem-2016-0281

[vi] Bisschop PH, Sauerwein HP, Endert E, Romjin JA. Isocaloric carbohydrate deprivation induces protein catabolism despite a low T3-syndrome in healthy men. Clinical Endocrinology 2001 Jan;54(1):75-80

[vii] Spaulding SW, Chopra IJ, Sherwin RS, Lyall SS. Effect of caloric restriction and dietary composition of serum T3 and reverse T3 in man. Journal of Clinical Endocrinology and Metabolism 1976 Jan;42(1):197-200. Doi: 10.1210/jcem-42-1-197

[viii] Nuttall FQ, Gannon MC. The metabolic response to a high-protein, low-carbohydrate diet in men with type 2 diabetes mellitus. Metabolism 2006 Feb;55(2):243-51. Doi: 10.1016/j.metabol.2005.08.027

[ix] Hendler R, Bonde AA 3rd. Very-low-calorie diets with high and low protein content: impact on triiodothyronine, energy expenditure, and nitrogen balance. American Journal of Clinical Nutrition 1988 Nov;48(5):1239-47. Doi: 10.1093/ajcn/48.5.1239

  1. Reply
    Shelley November 27, 2020 at 4:08 am

    Can you please quit advising people to consult their doctor when anything nutrition is involved? Doctors know very little, if anything at all about nutrition. I had a doctor who always had a heater under her desk, driving me nuts when I would go in her office because it was too hot. It just so happened that I had to advised my licensed PCP what to eat to alleviate her anemia.

  2. Reply
    Davide June 13, 2019 at 1:00 pm

    What do we know about that “study” that claims to link the Keto diet to a decrease in Thyroid function? The limited information available on that study doesn’t allow us to know if:

    – The diet was providing an adequate amount of calories (KD is not about caloric deficit, at all).
    – The composition of the diet
    – How strictly the sample was actually monitored

    The composition of the diet is of particular importance here. Up till now, the vast majority of studies on the effects of low-carb, high-fat diets on thyroid health have used high-PUFA high-fat diets. Could this confound the results? Yes.

    It turns out that linoleic acid suppresses thyroid signaling. So, before making blanket claims that KD is detrimental for thyroid health maybe some more informed data collection should be performed and made available.

    What do we know so far about KD, especially when associated with Intermitted Fasting, is that it represents a very healthy and balanced life style, that promotes cellular regeneration, increase in BMR, low insulin levels and overall health.

    So, thanks but NO thanks.

    And NO, breakfast is not the most important meal of the day; On the contrary; In the morning cortisol levels and insulin sensitivity are very high and eating breakfast can only make things worse. Skipping breakfast (and thus increasing the fasting window from the last meal) promotes a metabolic boost, increase in GH production and gut health.

    The Americal Journal of Clinical Nutrition published a study made in 2014 that, contrary to the one you link, is freely accessible here:

    The study already showed that there’s no metabolic advantage (not a single one) in having breakfast. Not only that, having breakfast increases the overall presence of glucose in the blood stream (hello insulin resistance!). Good luck with that.

    Restricting (not limiting) the feeding window is one of the most important discoveries in nutrition made in recent times that, fortunately, the Medical establishment is starting to recognize and promote.

  3. Reply
    Prabhmeet March 9, 2019 at 4:40 pm

    Shall i take keto tablets in hypothyroid ??? Is it safe ?? Is it helpful in loosing weight fast???

  4. Reply
    Jan January 4, 2019 at 3:58 pm

    Ketogenic diets, Intermittent Fasting and ‘calorie restriction’ are NOT the same. On a Ketogenic diet, one typically consumes more fat, protein and low sugar vegetables and less carbohydrates. With Intermittent fasting, what changes is WHEN you eat, not how much you eat. Calories do not typically come into play with either. I struggled with HT and being chubby despite working out religiously for 8-10 hrs weekly for 25 years. I am now post menopausal with HT. With the inclusion of more healthy fats and less than 20 gr of carbs daily, my endo has REDUCED my thyroid meds, I sleep better, have far fewer HT symptoms (which never completely went away even with the meds), reduction in carpal tunnel issues and beautiful definition of my muscles. And my hair is GLORIOUS, which it never was on thyroid meds only. So, sorry Charley. My endo is really happy with me and my thyroid and encourages me to keep up the good work.

    • Reply
      Makala August 2, 2019 at 10:50 pm

      Wow Jan…I sense some hostility in your comment. What works for you may not work for other. I am hypothyroid. I can assure you that my gluten intolerance and past dalliances with low carb made my situation worse. Now, I’m happy to say that with supplements and a healthy diet in moderation (which includes carbs), I feel great and have lost weight. I’m not into these crazy fad diets anymore such as Keto. Hey if it floats your boat…do it. Time will tell (and I don’t mean short term). Please don’t push your results as the be all and end all for everyone.

    • Reply
      Suzanne July 16, 2019 at 1:11 pm

      Hi Jan,
      I am encouraged by your comments and want to know which you do Keto or intermittent fasting. I am also interested in what thyroid meds you take. I think that also may make a difference in how the diet affects our health. Thank you.

  5. Reply
    Timothy James Bauman August 16, 2018 at 8:34 pm

    Thank you for this well researched and well presented article. Having secondary hypothyroidism is a struggle especially with weight management, response to high intensity exercise and dietary needs. This article has given me much needed information to move forward with a plan to manage and correct the affects of HT.

    Many thanks!

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