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Does Thyroid Medication Interfere with Ketosis?

Learn what you need to know about eating a keto diet if you take thyroid medication for hypothyroidism.
Does Thyroid Medication Interfere with Ketosis?
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The ketogenic diet has become a buzzworthy diet in the past few years. One of the biggest successes of the keto diet is that it can help many people lose weight. For others, it has helped boost energy levels, improve cholesterol levels, and control blood sugar. However, like all diets, it is essential to talk to your doctor before trying keto, especially if you have a thyroid condition like hypothyroidism. Here’s why.

What is ketosis?

Ketosis is a metabolic state characterized by the presence of elevated ketones in your bloodstream. People can achieve a ketogenic state by severely restricting carbohydrate intake. Carbohydrates break down into a quick, useable form of energy called glucose. The digestive system pulls glucose from our food to fuel our cells. However, when we do not have enough carbohydrates to support cellular energy needs, the liver produces ketones from fat, serving as a fuel. 

The ketogenic diet helps you enter a state of ketosis by limiting the amount of carbohydrates you eat. Instead, you get fuel from foods higher in fat content (like avocados) and moderate protein intake. 

Eating too many carbohydrates causes your body to store unused glucose as fat. Additionally, it can also lead to insulin resistance, one of the biggest causes of type 2 diabetes and obesity. 

People can see if they are in ketosis by testing their urine or blood for ketones. If you are positive for ketones, that means you are burning fat and producing less glucose. Ultimately, less glucose means you are also producing less insulin, which can be good and bad for people with a thyroid condition.

Potential problems with the keto diet and thyroid conditions

Keto diets can offer tremendous benefits for people with thyroid conditions. However, there are some concerns that you should be aware of if you are considering this diet and are taking thyroid medication.

Firstly, a reduced amount of insulin may affect your ability to convert the inactive thyroid hormone thyroxine (T4) to the active thyroid hormone triiodothyronine (T3). This conversion occurs in the liver and is necessary because it turns the thyroid hormone into its active form. When insulin levels are too low, it can inhibit the liver’s ability to convert T4 to T3, thus reducing the availability of usable thyroid hormone in the body.  

Secondly, prolonged ketosis can force the body to accumulate acid, which can spur inflammation. Most people with thyroid diseases already suffer from chronic inflammation, especially if they have Graves’ or Hashimoto’s disease--two thyroid conditions caused by autoimmune processes. 

Because of these two primary concerns, people with thyroid conditions who try the keto diet sometimes struggle with worsening thyroid-related symptoms like a Hashimoto’s flare-up. They may also be more prone to side effects like the keto flu, a cluster of flu-like symptoms that some people experience within the first few weeks of eating a keto diet.

Furthermore, it can be harder to regulate thyroid hormone levels, especially when you are just getting started on the diet. 

How does a ketogenic diet interfere with thyroid medication?

Most people with a thyroid condition like hypothyroidism require thyroid medication to help normalize thyroid hormones. It takes several weeks to months to find the correct dose of thyroid medication for each individual. Once you find the correct dose, it is essential to stick with it unless certain factors change in your body, such as having significant weight changes or starting a new diet. 

Because ketosis can decrease your liver’s ability to convert T4 to T3, some people find their thyroid hormone levels change even when they take thyroid medication. Also, because inflammation may worsen with ketosis, you may feel unwell unless you make changes to your medication regime.

People taking thyroid medication should never make changes to their dose or the type of medication they are taking without consulting their doctor first. 

How to use a modified keto diet for hypothyroidism

There is no one-size-fits-all dietary approach for anyone, especially people with a health issue like hypothyroidism. For many, a keto diet can be a valuable tool for curbing weight gain, losing belly fat, and decreasing appetite. But, as we have seen, there may be some concerns with this diet for people with thyroid disorders. Therefore, it can be helpful to tailor the diet to help suit your individual needs.

We know that too many carbohydrates can spike your blood sugar, cause weight gain, and lead to insulin sensitivity. So, curbing carbohydrates is a useful step in managing weight and warding off health conditions. But inflammation is still a concern with the keto diet. 

To decrease the side effect of inflammation from ketosis, boost your intake of anti-inflammatory foods like leafy greens or foods that contain vitamin D and omega 3’s (like salmon). You can add these foods to your regular meals and even slip them into smoothies. 


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Aside from modifying the keto diet to include anti-inflammatory foods, it is helpful also to consider:

Removing dietary triggers 

Dietary triggers can worsen inflammation or interfere with your thyroid function. Many people with thyroid diseases like Hashimoto’s try strict elimination diets like the autoimmune protocol to find their triggers. 

Trying intermittent fasting

Intermittent fasting can encourage significant metabolic changes to occur in your body. 

Before making changes to your diet, it is necessary to consult your thyroid doctor. Understanding the nuances of various diets can be challenging. It may also benefit you to meet with a thyroid nutritionist to maximize your nutrient intake while reaching your health goals. 


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Julia Walker, RN, BSN

Clinical Nurse

Julia Walker, RN, BSN, is a clinical nurse specializing in helping patients with thyroid disorders. She holds a Bachelor of Science in Nursing from Regis University in Denver and a Bachelor of Arts in the History of Medicine from the University of Colorado-Boulder. She believes managing chronic illnesses requires a balance of medical interventions and lifestyle adjustments. Her background includes caring for patients in women’s health, critical care, pediatrics, allergy, and immunology.

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