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The Keto Diet and Your Thyroid: How it Impacts Your Hormones
The Keto Diet and Your Thyroid: How it Impacts Your Hormones
Base Medical Team avatar
Written by Base Medical Team
Updated over a week ago

Take a moment and consider the ‘ketogenic (or keto) diet.’ What comes to mind? If you’re like most people, you probably associate the ketogenic diet with fat loss.

The keto diet has gained immense popularity in recent years and is often touted as a magic bullet for weight loss. But the simple truth is the keto diet is not for everyone. Regardless of the eating pattern you use, it is essential to consider your unique needs; this is especially true if you have a thyroid disorder or are at risk for developing one.

The Keto Diet and Your Thyroid:  How it Impacts Your Hormones


  • The ketogenic diet is a low-carb, high-fat, and moderate-protein pattern of eating.

  • Many people use the ketogenic diet to achieve their health goals, such as losing weight.

  • The keto pattern of eating has the potential to detrimentally impact hormone balance, particularly that of the thyroid hormones.

  • If you have a thyroid condition and want to try the ketogenic diet, at-home lab testing can help you find a keto modification that meets your needs.

The Keto Diet: A (Very) Brief History

The keto diet was originally used to treat childhood epilepsy. As science advanced and anti-epileptic medications became more available, the diet faded in popularity, until recently! Internet search termsrelated to the ketogenic diet started to see a dramatic increase in the 2010s, a fact likely attributable to celebrities and social media influencers shouting from the rooftops the weight-loss results they saw with the diet.

So, What is a Ketogenic Diet (in 30 Seconds)?

The ketogenic diet is a high-fat, moderate-protein, and low-carbohydrate pattern of eating. If you’re wondering how to start keto, the typical macronutrient ratio looks like this:

  • 55 to 60% fat

  • 30 to 35% protein

  • 5 to 10% carbohydrate

For the standard 2000 calorie diet, you’d be striving to have no more than 50 grams of carbohydrate per day. For reference, a bagel has about 50 grams of carbohydrate.

While cutting out carbs may not sound all that fun, there are some research-backed benefits to doing so. From helping with blood sugar control, to improving lipid panels, to helping get rid of those pesky love handles, the keto diet can certainly have a positive impact on your health.

What is Ketosis, and How Do You Know if You’re in It?

The keto diet mimics a fast and deprives your body of its preferred source of energy: The lovely carbohydrate. When you restrict dietary carbs, you use glycogen stores of carbs in your liver and muscles. Once those stores are gone, typically after about 12 hours, you can then enter… ketogenesis.

Ketogenesis is the reason the keto diet is known to burn fat; in this phase of metabolism, your body’s fat stores are used to supply energy to the rest of your body. The fat stores are accessed to createketone bodies which are then used for energy.

Your heart, muscle tissue, kidneys, and brain can use ketone bodies for energy, but your red blood cells and liver cannot. Ketone bodies also have cell-protective antioxidant properties!

Basically, ketosis is your body’s fail-safe against starvation. When there aren’t enough carbohydrates in your diet, your metabolism switches to burn your energy stores so you can continue living. Thank you, biology!

To know if you’re in ketosis, watch out for the ‘keto flu,’ which includes symptoms like:

  • Brain fog

  • Sore muscles/cramps

  • Dizziness

  • Keto-breath (which stinks)

  • Headache

  • Fatigue

Symptoms are typically short-term and last a number of days; be sure to stay hydrated as this can help stave off some symptoms. More accurate ways to determine if you’re in ketosis include ketone urine strips, breath tests, and blood tests.

What Your Thyroid Does and Why it Matters

Located on the front side of your neck and below your voice box, your thyroid is a tiny gland that plays a huge role in the development of your body and maintenance of your metabolism. It constantly regulates your body’s functions including (but not limited to):

  • Heat regulation

  • Your heartbeat

  • Your metabolism

  • The speed of digestion

  • Muscle contraction

Your thyroid secretes two hormones into your blood stream:

  • T4 (tetraiodothyronine): The inactive form of T3; it converts to T3 as needed.

  • T3 (triiodothyronine): The biologically active hormone that plays a role in the metabolism for all your cells and manages the functions described above (in addition to many, many others)!

In short, T3 tells your cells how quickly to work. If T3 levels are too high, your cells work more quickly; you may experience a faster heartbeat, and you’ll likely be diagnosed with hyperthyroidism. Too little T3 can lead to hypothyroidism where your cells operate more slowly (you might have a slower heartbeat, for example).

Keto and Thyroid: Is Keto Safe for Someone With a Thyroid Condition?

The keto diet is not the best hormone balancing diet and does have the potential to detrimentally alter thyroid hormone levels. Research indicates periods of starvation (which the keto diet mimics) as well as weight loss from the keto diet can lower T3 levels, leading to weight gain!

From a biological standpoint, it makes sense for your body to lower T3 production when it senses caloric/carbohydrate restriction: Lower T3 means less energy expenditure. When your body perceives a ‘famine,’ your metabolism downregulates to become as efficient as possible to keep you alive as long as possible.

If you have a thyroid condition, you may see initial positive results on the keto diet. But over time, you may develop symptoms such as increased tiredness and weight gain. These symptoms may be a result of your body’s response to the low carb diet, which is to lower T3 production.

While there are potential risks for going keto with a thyroid condition, there are steps you can take to increase your chances of success on the diet.

How to Stay on Top of Your Thyroid While You’re Keto

There is no ‘one-size-fits-all’ rule when it comes to determining the safety of the keto diet if you have a thyroid condition. This is simply because your body is incredibly unique! For this reason, it is essential to be in-tune with how you are feeling when making any lifestyle change like starting a keto diet.

If your energy levels are normal, you’re able to think clearly, and you’re making progress with your weight goals, you likely don’t have much to worry about with the keto diet.

However, if you are experiencing adverse symptoms that last a long time, such as fatigue or an inability to lose weight, that is an indication your thyroid hormones might be unbalanced. If this happens to you, the best way to see if your hormone levels are off is to get a blood test.

How to Modify the Keto Diet for Thyroid Health Without Leaving Ketosis?

At-home lab testing can give you direct insight into the impact the keto diet has on your thyroid hormone levels. By tracking the impact different adjustments have on your bloodwork, you can find your optimized ketogenic diet. Some adjustments you can make include:

  • To use intermittent fasting

  • To adjust the carb, protein, and fat ratios

  • To reduce consumption of foods you may be sensitive to such as gluten, dairy, or soy

  • To balance your lifestyle all around, including your sleeping pattern, exercise, and stress management

In as little as one month you can see the impact a lifestyle change has on your thyroid hormone levels. Over time, you will be able to either determine keto is not for you or find a modified keto pattern that works for you and gets you the results you want to see!

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