The Most Common Low Vitamin Levels with Hypothyroidism

There are certain low vitamin levels that are common in existing alongside hypothyroidism, especially autoimmune hypothyroidism, as it can be tied in to gut health and how well you absorb certain vitamins and nutrients. Problems with intestinal permeability can lead to numerous deficiencies.

Below are the most common vitamin deficiencies that I suggest you check out if you’re still feeling unwell. You can also find a list of recommended supplements here, but please do not supplement unless you’ve confirmed low/deficient levels. 

Iron and Ferritin

Perhaps the most common are low levels in iron or ferritin (stored iron), which can lead to dry skin, heavy fatigue, poor stamina, depression and even pale skin and dark bags under the eyes. I’ve been anaemic a few times myself and it presented with all of these signs. Iron deficiency also impairs thyroid hormone synthesis.

It is worth bearing in mind that as hypothyroidism mainly affects women, many thyroid patients will have low levels of iron/ferritin due to period issues such as heavy or long periods.


Selenium is not naturally occurring in the body, but is a trace mineral found in food and soil. It is vital for immune response and thyroid function, including conversion of thyroid hormone T4 to T3, making it essential for good metabolic function. With low selenium levels, you could have symptoms such as brain fog and decreased cognitive functions, as well as a lack of energy and blood results that look ‘OK’, even if you feel unwell. You could also have low Free T3 as a sign that selenium is low or deficient, causing not enough T4 to T3 conversion.


Being low in B12 can cause tiredness, fatigue, a sluggish metabolism and poor adrenal health. Vitamin B-12 and folic acid are both important for energy and heart protection. B12 is also needed in order to make TSH, a hormone secreted by the pituitary gland that instructs the thyroid on how much thyroid hormone to make. People with hypothyroidism often seem to struggle to absorb B12 and low levels in it can cause mental illness, various neurological disorders, neuralgia, neuritis and bursitis.


Low Vitamin D levels seem to be increasingly common, not just among thyroid patients but the general population as a whole. Low levels in this vitamin can cause depression, back pain, fatigue and poor immune system function. A Vitamin D deficiency can also stop T3 from activating your cell to increase metabolic rate and energy levels. Vitamin D has also been shown to lower thyroid antibodies.


A Vitamin A deficiency can stop T3 from activating your cell to increase metabolic rate and energy levels but it is also needed for good immune system function. Vitamin A must be accompanied by protein to make it available to the body, so if you are on a low protein diet, you may be deficient in this.  If you are low on Vitamin A, your ability to produce TSH is limited. This vitamin is also required by the body to convert T4 to T3.


An antioxidant, vitamin E is a fat-soluble vitamin important for many processes in the body, including producing TSH.


Zinc is needed in order to make TSH, a hormone produced by the pituitary to instruct the thyroid gland in making thyroid hormone. It also plays a role in the functioning of the immune system and the conversion of T4 to T3.


Magnesium is needed in order to make TSH and for the conversion of T4 into T3. It seems that a diet high in refined food and caffeine will encourage magnesium loss. Supplementing magnesium can also help cramps, energy and aches and pains, common symptoms of hypothyroidism.


Without question, iodine is the most controversial mineral when it comes to thyroid health. Some say to supplement, others say not to. It is required by the thyroid gland in order to make the thyroid hormone T4, though, and not enough Iodine can actually cause hypothyroidism. As recommended by Natural Endocrine Solutions here, for anyone who wants to try supplementing iodine, I’d first recommend getting your levels  tested, and then if it shows you’re iodine deficient, I recommend starting with a small dosage, along with taking antioxidants such as selenium and vitamin C, and magnesium.

You can also find a list of recommended supplements here, but please do not supplement unless you’ve confirmed low/deficient levels. Doing so can do more harm than good. 

Rachel, The Invisible Hypothyroidism

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