Should You Try the Keto Diet for Thyroid Function?

Keto is everywhere right now, and for good reason. The research on ketogenic diets is compelling, from weight loss and improved energy to reduced inflammation and immune support. If you have Hashimoto's, Graves', or any other form of thyroid dysfunction, it is natural to wonder whether keto might help you, too.

The answer is nuanced. While keto has genuine benefits for certain autoimmune conditions, it carries specific risks for thyroid function that are worth understanding before you make the switch. I have seen this play out in my clinic, and I want to make sure you have the full picture before committing to a strict low-carb approach. If you are looking to support your thyroid naturally, while you read on, the Hashimoto's Health Bundle and The Myers Way® Multivitamin are two places to start.

What Is the Keto Diet?

The ketogenic diet is a very low-carb, high-fat, moderate-protein diet. On a true keto diet, carbohydrates are restricted to roughly 20-30 grams per day, about 5% of daily calories. By comparison, a standard diet derives 45-60% of daily calories from carbohydrates.

When your carbohydrate intake drops this low, your body can no longer rely on glucose as its primary fuel. Instead, it enters a metabolic state called ketosis, in which stored fat becomes the primary energy source. Research shows that keto can support a healthy immune response and increase glutathione levels, which are often low in people with autoimmunity. (1) For some autoimmune conditions, this is a meaningful benefit. For thyroid conditions specifically, there is more to consider.

How the Keto Diet Affects Thyroid Function

This is where the conversation gets important. The parts of your brain responsible for regulating thyroid hormone production, the hypothalamus and the pituitary gland, require glucose to function optimally. (2) TSH, or thyroid-stimulating hormone, is itself partly composed of glucose molecules.

When carbohydrate intake drops severely, this regulatory system can become impaired. Research shows that strict carbohydrate restriction significantly reduces Free T3 (FT3), your active thyroid hormone, and increases Reverse T3 (RT3). (3)

Here is why that matters:

When RT3 is elevated, it competes with FT3 at the receptor level, meaning even if your thyroid is producing hormones, your cells may not be able to use them effectively. This is a meaningful concern for anyone already managing thyroid dysfunction. 

Keto and Hashimoto's: What to Know

If you have Hashimoto's, your thyroid is already underproducing hormones in a state of hypothyroidism. Adding a strict keto diet to the equation can further reduce FT3 and compound existing symptoms. Watch for these signs that keto may be worsening your thyroid function:

• Increased fatigue or sluggishness
• Worsening brain fog
• Unexplained hair loss
• Weight gain despite dietary changes
• Increased cold intolerance

That said, a modified keto approach, maintaining at least 50 grams of carbohydrates per day rather than the strict 20-30 gram threshold, has shown no adverse effects on thyroid hormone production. If you are committed to a low-carb diet and have Hashimoto's, this modified version is worth exploring under the guidance of a functional medicine physician.

The same caution applies if you have Graves' or any other form of thyroid dysfunction. I always recommend monitoring your thyroid labs closely if you are experimenting with significant dietary changes.

Keto and Hypothyroidism: Proceed With Caution

Even without an autoimmune component, hypothyroidism and strict keto can be a challenging combination. An underactive thyroid already slows your metabolism, and the reduction in FT3 that accompanies severe carbohydrate restriction can deepen that metabolic slowdown. Some people on keto with hypothyroidism report worsening fatigue, constipation, and difficulty losing weight, which are the opposite effects they were hoping for.

If you are on supplemental thyroid hormone and following a strict keto diet, your dosage may need to be reassessed as your thyroid markers shift. This is not a reason to avoid all carbohydrate reduction; it is a reason to approach it thoughtfully and work with a physician who understands the thyroid-glucose relationship.

Keto Diet for Autoimmune Disease: A Broader Look

It is worth noting that keto's anti-inflammatory effects and glutathione-boosting properties are genuinely beneficial for autoimmunity broadly. For conditions such as rheumatoid arthritis, lupus, or multiple sclerosis that do not carry the same thyroid-specific risks, keto may be a more appropriate dietary strategy.

The key distinction is the glucose-dependent HPT (hypothalamic-pituitary-thyroid) axis. Thyroid-specific autoimmune conditions, Hashimoto's and Graves’, carry an additional layer of risk that other autoimmune conditions do not. That does not make keto off-limits, but it does mean the approach requires more precision and monitoring.

What to Do Instead: The Thyroid Diet That Actually Works

The single most impactful dietary change you can make for thyroid dysfunction is not cutting carbs; it is removing toxic and inflammatory foods. Specifically, gluten must be the first to go.

Gluten shares a structural similarity with thyroid tissue. This means that when your immune system produces antibodies against gluten that has entered your bloodstream through a leaky gut, it can mistakenly attack your thyroid as well -- a phenomenon called molecular mimicry. For anyone with Hashimoto's or Graves', this cross-reactivity can be a significant driver of ongoing immune activity.

The thyroid diet I recommend removes:

• Gluten -- permanently
• Dairy -- particularly casein, which has a similar molecular structure to gluten
• Corn, soy, and sugar
• Grains and legumes
• Processed foods and hidden inflammatory ingredients

In their place, you focus on non-starchy vegetables, quality proteins, and healthy fats, an anti-inflammatory foundation that supports thyroid health without the risks of extreme carbohydrate restriction.

I walk through this in detail in "The Thyroid Connection," including a complete 28-day thyroid diet plan. The Myers Way® framework addresses the root causes of thyroid dysfunction: diet, gut health, toxins, infections, and stress, without the downsides that strict keto can introduce.

Supporting Thyroid Function Naturally

Diet is foundational, and targeted nutritional support can meaningfully complement it. Two supplements I recommend for those managing thyroid dysfunction are:

The Myers Way® Multivitamin is physician-formulated and comprehensive, supporting healthy thyroid and adrenal function. It includes key nutrients essential for thyroid health, such as selenium, iodine, B vitamins, and vitamin D, which are commonly depleted in those with thyroid dysfunction and difficult to obtain in adequate amounts from diet alone.

Adrenal Support is worth considering if stress is a factor in your thyroid picture. The adrenal-thyroid connection is one of the most overlooked aspects of thyroid health. Chronic stress elevates cortisol, which suppresses thyroid hormone conversion and can worsen both Hashimoto's and hypothyroid symptoms. Adrenal Support contains a blend of adaptogenic herbs, including Rhodiola Rosea, Panax Ginseng, Eleuthero, and Ashwagandha, to support healthy cortisol levels and a balanced stress response.

For a comprehensive starting point, the Hashimoto's Health Bundle brings together targeted support for those navigating Hashimoto's specifically.

The goal is never to chase a diet trend. It is to get to the root of what is driving your thyroid dysfunction and give your body the support it needs to find balance. That is The Myers Way®.