Thyroid Brain Fog

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Originally published on 29th April 2016 
Last updated on 26th November 2019

Thyroid brain fog is real. Oh, it’s real alright. You can read the lighter side of my brain fog experiences here, but in this post, I’m going to explore how and why thyroid patients experience it among their many other symptoms.

What is Brain Fog?

Brain fog is often described as feelings of mental confusion or lack of mental clarity. The phrase comes from the feeling of a fog that reduces your ability to think clearly. It can feel like a mental block. It can cause a person to become forgetful, detached and discouraged and even depressed as a knock on effect.

Brain fog is a common symptom of thyroid problems, particularly hypothyroidism.

Read how thyroid patients commonly describe their brain fog here.

What Causes Thyroid Brain Fog?

Low Thyroid Hormone Levels 

Thyroid hormones T3 and T4, used by the brain, have major influences over virtually every brain activity. So if a thyroid patient doesn’t have enough of these thyroid hormones in their body, brain fog often occurs, to varying degrees.

At times, mine was so severe that it seriously impacted my ability to work. I could read an email ten times and it still wasn’t registering in my mind.

Ensure that both your Free T3 and Free T4 are optimised and not just ‘normal’, ‘fine’ or ‘in range’.

Thyroid hormone, particularly T3, has an important role in the health and optimal functioning of your brain, including: cognitive function, the ability to concentrate, mood, memory and attention span. This explains why we can experience symptoms such as brain fog. T3 interacts with brain receptors and makes the brain more sensitive to chemicals such as serotonin and norepinephrine, which affects your alertness, memory, mood and emotion.


Inflammation in the body can mean all sorts of things, from a leaky gut, to gluten sensitivity and Hashimoto’s, and brain fog could be an indication of inflammation in the brain.

Dr Datis Kharrazian also comments on how Hashimoto’s, which around 90% of hypothyroid patients have [1], can cause inflammation in the brain, leading to symptoms like brain fog. I watched a seminar on this at the Healing Hashimoto’s summit, 13th-20th June 2016.

Being hypothyroid means you have a high chance of also having an autoimmune disease like Hashimoto’s, so cutting out gluten may also help with inflammation.

Mental Health 

Since depression can also cause symptoms of brain fog, receiving adequate treatment for that and treating any underlying conditions is also important. Many thyroid patients are also on antidepressants. My depression was caused by an inadequately treated thyroid problem, so once my medication was right for me (switching to NDT), my depression lifted.

Vitamin Levels 

Explore Vitamin B12, D, iron, ferritin etc. too to rule out other causes for brain fog and similar thyroid symptoms.

Some thyroid patients also swear by magnesium supplementation for improving brain fog.

Poor Gut Health

I experienced an impressive reduction in brain fog after overcoming candida (yeast overgrowth) and gut permeability with a functional medicine practitioner. With leaky gut, the intestinal barrier of the gut becomes permeable from hypothyroidism, infections, food intolerances (especially gluten) or even stress, allowing food particles to slip through and circulate round the rest of the body. This can lead to your microglia, who work to defend your central nervous system, going in to high alert – leading to inflammation in the brain.

Addressing any gut issues is crucial for overall thyroid health, and the first step many thyroid patients make to improve this is by removing offending foods from their dit, such as gluten and dairy, which alone can improve brain fog a lot.

A UK test for Candida can be found here. and a US test here.

Blood Sugar Imbalances

Symptoms of blood sugar issues can include headaches, feeling faint and dizzy, feeling hungry again quickly after eating, feeling tired, grouchy, irritable and foggy minded.

One of the simplest things you can do to improve any thyroid symptoms you have is to learn how to keep your blood sugar balanced. Since realising that I needed to adjust my diet to allow more protein and fat (and less sugar and carbs) in order to balance my blood sugar better, my low blood sugar bouts, irritable moods, groggy feeling, brain fog and slumps are gone.

Healthy fats play a big role in our mental health, mood and brain function. Good sources of fat include olive oil, sesame oil, avocados, olives, nuts, seeds, peanut butter, flaxseed, salmon, chia seeds, eggs and even seed butter.

I also ensure I consume enough protein with every meal and snack, in order to keep my blood sugar levels balanced; sources of protein can include meats, cheese, eggs, nuts, seeds, yoghurts, beans and legumes.

We should aim to eat every two to three hours to keep blood sugar levels balanced. Going long times without food, such as fasting, can place extra stress on the adrenal glands. Never skip meals.

What Helped Remove My Brain Fog

Going gluten-free dramatically improved my brain fog, but things like addressing low iron levels and low Vitamin D levels also helped. As well as addressing my gut health, diet and eating to better balance blood sugar levels.

Keep nudging your doctor for more reasons as to what is causing your brain fog if you still have no joy with any of the above tips. It’s often one of the most debilitating symptoms of being hypothyroid.

Do you experience thyroid brain fog?

Be Your Own Thyroid Advocate Book CoverSee also:

The book Be Your Own Thyroid Advocate: When You’re Sick and Tired of Being Sick and Tiredwhich builds on this article in detail and covers the simple things you can do to resolve thyroid symptoms.

You can click on the hyperlinks in the above post to learn more and see references to information given, but more reading and references can also be found at:



If you found this article beneficial, please take a moment to share it so we can help others get better with hypothyroidism and Hashimoto's, whilst also raising awareness.

10 thoughts on “Thyroid Brain Fog

  1. I always spend half an hour to read your site’s articles daily along with a cup of coffee!

  2. Hahaha, gasp. This is what we get when we go to the doctor, ignorant healthcare workers, who have not used one hour of their time to do their own research and comparison, and they are recommending vaccines, scary.

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  5. I found no explanation for my brain fog but your article makes sense.
    I actually tried this weeks ago (removing gluten) and it helped my memory and thought processing however cutting down grains left me fatigued as I couldnt get the energy from other foods. This time I will try potatoes instead but those irritate my gut. I assume it is less bad than gluten in driving inflammation.

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