Thyroid Basics

Understanding Brain Fog

By: Mary Shomon, Thyroid Expert

Average reading time: 2 minutes

Q & A with Mary Shomon

Thyroid expert, advocate, and NY Times bestselling author

Brain fog is one of the most common complaints of thyroid patients far and wide. Physicians often call it ‘cognitive impairment.’ For those who suffer from it, it can feel like your head is floating in the clouds and your own mind is betraying you, as you struggle to recall things like, “Did I already ask that question?” Did I remember to turn off the oven / feed the dog / take my meds / etc.? What was I looking for again? What was I saying? What’s that word again?” 

Not only can it be a limiting factor in our professional and personal lives as we struggle with memory, cognition, and acuity; it can be downright scary. As Mary Shomon explained, “It’s frightening for a woman over 60 to experience memory or focus issues. The first thought is often Alzheimer’s or dementia. What is far more likely, however, is an undiagnosed case of a common problem: hypothyroidism.” 

We spoke with Mary, our Thyroid Refresh resident thyroid expert, about this frustrating affliction, and what can be done to lessen and lift persistent brain fog.  


What is thyroid brain fog?


Imagine calling your child by the wrong name, forgetting your phone number or zip code, or realizing you have no idea where you are going while driving. These frightening memory lapses are common in people with thyroid problems. Thyroid patients call it brain fog, and doctors call it “cognitive impairment”—either way, it’s an all-too-common thyroid symptom.

The thyroid is a small gland with a big job: to help deliver energy to organs, glands, and cells throughout your body. When your thyroid is underactive (hypothyroidism), the energy shortage slows everything down, including your brain. The result is brain fog, along with other frustrating symptoms like fatigue, weight gain, and depression.

‘It may seem like a ‘no-brainer,’ but doctors should immediately suspect hypothyroidism when a woman complains about problems with memory or concentration.”
– Mary Shomon


What types of thyroid conditions are most commonly associated with brain fog?


Brain fog is a common symptom of both hypothyroidism and Hashimoto’s thyroiditis, an autoimmune disease that causes hypothyroidism. Hypothyroidism is more widespread than you may realize, affecting about 20% of women in the U.S. And, scarily, the majority of people with hypothyroidism haven’t yet been diagnosed!


When you are struggling with memory and thinking problems, you’d think your doctor would automatically check your thyroid. Unfortunately, many doctors assume that cognitive impairment is typical for women, especially after childbirth, during menopause, or after age 60.


What does it feel like?


When you have brain fog, there are times when it’s hard for you to focus. Concentrating can be more difficult and even exhausting. It may take more time than usual for you to process information or react. You may feel unmotivated, forgetful, or spacey. Your memory for names, numbers, and directions could be unpredictable. You may even mix up words, or have trouble recalling a common word.



Can it be treated?


If you have brain fog, your first step is to see your doctor for a thorough check-up, including a thyroid exam. Your doctor should take your medical history, examine your thyroid, and order a complete thyroid blood test panel. If your doctor diagnoses you with hypothyroidism, treatment with a prescription thyroid drug may quickly and easily resolve your brain fog.


What should people with thyroid issues do if they experience cognitive impairment?

If you are already being treated for hypothyroidism but still have brain fog, you may need more aggressive thyroid treatment. Talk to your doctor about an increase in your thyroid medication or adding a medication like Cytomel to your standard levothyroxine (Synthroid, Levoxyl) treatment. You may need to switch to a natural desiccated thyroid drug like Armour or Nature-throid to resolve your brain fog.

Are you still struggling with brain fog after optimal hypothyroidism treatment? Lack of sleep is a major brain fog trigger, so make sure you get at least 7 to 8 hours of sleep each night. Gluten sensitivity can also be a trigger, and some thyroid patients report that going gluten-free greatly improved brain fog symptoms.

If that doesn’t work, it might be time to speak with your healthcare provider about supplements that can help with memory and concentration.

Up Next: The Importance of Sleep and Sleep Hygiene for Thyroid Patients

Imagine calling your child by the wrong name, forgetting your phone number or zip code, or realizing you have no idea where you are going while driving. This is what thyroid brain fog feels like.
– Mary Shomon



About the Author

Mary Shomon is a patient advocate and New York Times bestselling author of 13 books on health. Mary has been researching, writing and teaching about thyroid disease, hormonal health, weight loss, and autoimmune disease for two decades. In addition to her books, you can find her writing at and, and catch her PBS Healthy Hormones television specials. Follow Mary on Facebook.