Monitor an underactive thyroid (hypothyroidism)

Monitor and improve your thyroid function with a home blood test, personalised insights, and GP advice.


What is an underactive thyroid?

Your thyroid gland produces hormones that help control your metabolism. These hormones are:

  • thyroxine (T4)
  • triiodothyronine (T3)

If your thyroid gland doesn’t produce enough of these hormones, it’s called hypothyroidism (or an underactive thyroid).

Symptoms of an underactive thyroid

The lack of thyroid hormones can “slow down” many of your bodily processes. This can lead to symptoms like:

  • weight gain
  • extreme tiredness
  • irregular periods with heavy bleeding
  • brittle hair or hair loss
  • difficulty concentrating
  • low mood
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Monitor an underactive thyroid with a blood test

A blood test can measure your thyroid hormone levels to see if it’s underactive. It can also check to see if you’re getting the nutrients you need to support your thyroid function.


Thyroid hormones

Thyroid hormones include T3 and T4. Another important hormone is thyroid-stimulating hormones (TSH) — this controls the production of T3 and T4. If your thyroid gland is underactive, your T3 and T4 levels drop. While your TSH levels increase to try to stimulate your thyroid to produce more hormones. 


Thyroid antibodies

Thyroid antibodies can sometimes cause an autoimmune thyroid disease — where your body mistakenly attacks your thyroid gland. If this leads to an underactive thyroid, it’s called autoimmune thyroiditis. These antibodies include thyroid peroxidase antibody (TPO) and thyroglobulin antibody.


Vitamin B12

Vitamin B12 plays a key role in the normal functioning of the nervous system, and the formation of red blood cells. Vitamin B12 deficiency is commonly seen in people with an underactive thyroid. And increasing your levels might help to improve symptoms.



Folate (vitamin B9) is needed for a healthy liver, as well as healthy skin, hair, and eyes. An underactive thyroid has been linked to lower folate levels. If you’re deficient, symptoms include feeling tired, pins and needles, and shortness of breath.


Vitamin D

Vitamin D deficiency is linked to thyroid disorders. Some research suggests that low vitamin D levels can affect your immune function, which could increase your risk of an autoimmune thyroid disorder developing. A deficiency is also linked to tiredness, low mood, bone and muscle pain, as well as getting ill more often than usual.



If your iron levels are low it might affect your thyroid function. Some research suggests it can increase your risk of developing an underactive thyroid. It’s also thought that an underactive thyroid might contribute to iron deficiency anaemia.



An underactive thyroid has been linked to high blood glucose (sugar) levels — which can affect your risk of type 2 diabetes. A HbA1c test measures your average blood glucose levels over the last 3 months.



An underactive thyroid might make your body less effective at removing LDL cholesterol — the type of cholesterol that can increase your risk of heart disease. So it’s worth monitoring your cholesterol over time to help manage your risk.

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Emma has an underactive thyroid and wants to monitor her condition. She tracks her thyroid function and checks for any nutrient deficiencies linked to her condition.

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