blood tests

5 minute read

Tired and putting on weight? Check your thyroid with a home blood test

By Ashton Sheriff | Medically reviewed by Dr Jaskirt Matharu
fatigued man lying in bed

If you’ve been feeling more sluggish than usual and have noticed some unwanted weight gain, it may be worth taking a home blood test to check your thyroid function. Extreme tiredness (fatigue) can be caused by an underactive thyroid (hypothyroidism), which is a condition where the thyroid does not produce and release enough thyroid hormone into your body. 

Hypothyroidism, also known as an “underactive thyroid”, can also make your metabolism slow down and cause you to gain weight. Although it’s more common in women, hypothyroidism can affect anyone, meaning it’s important to check your thyroid function with a thyroid blood test regardless of your age, gender, or ethnicity. 

What does the thyroid do?

The thyroid is a small, butterfly-shaped organ in your neck that mainly helps to control your body’s metabolism. It does so by creating special hormones (known as T4 and T3) that tell your body’s cells how much energy to use.

But your thyroid can’t work its magic without a little assistance. It has a close relationship with your pituitary gland (a small gland in the brain) and they work together to keep your thyroid hormones in balance. 

If your pituitary gland detects that your thyroid hormone levels are too low, it’ll stimulate your thyroid to produce more of them and vice versa. It achieves this by producing its own hormone called TSH (thyroid-stimulating hormone) that interacts with the thyroid. This harmony between your thyroid and pituitary gland helps to keep your entire body in check, so it’s really important to make sure it’s functioning well with a blood test.

What is an underactive thyroid (hypothyroidism)?

Hypothyroidism, also known as an “underactive thyroid”, occurs when the thyroid doesn’t produce enough thyroid hormone. 

What causes an underactive thyroid?

In most cases, an underactive thyroid is caused by Hashimoto’s disease - an autoimmune condition that causes the immune system to attack the thyroid gland. It’s not understood what causes Hashimoto’s disease, but it’s known to be a hereditary condition (meaning it runs in families). 

Other things that can cause an underactive thyroid include:

  • Thyroiditis (inflammation of the thyroid).

  • Iodine deficiency.

  • Surgery or radiation therapy for hyperthyroidism. 

Underactive thyroid symptoms

Underactive thyroid symptoms may slip under your radar because they can often be mistaken for symptoms of other conditions. Fatigue is a common symptom of an underactive thyroid, but it can also be a symptom of anaemia, diabetes, and low testosterone. Unwanted weight gain is another symptom, but it can be difficult to tell if you’ve gained weight due to inactivity, lifestyle changes, or an underlying condition like an underactive thyroid. 

For this reason, it’s crucial that you have a health check up with a blood test if you experience symptoms of hypothyroidism. These include:

  • Depression.

  • Constipation.

  • Low sex drive.

  • Fatigue (feeling tired).

  • Unwanted weight gain. 

  • High cholesterol levels.

  • Being sensitive to the cold.

  • Skin and hair that feels dry and coarse. 

  • Frequent and heavy menstrual periods.

  • Developing a deeper and more hoarse voice.

  • The sensation of numbness and tingling in your hands.

  • Muscle weakness and soreness throughout your body. 

  • Not being able to focus or concentrate properly (“brain fog”). 

  • Physical changes in your face (including drooping eyelids, as well as puffiness in the eyes and face).

What’s the difference between an underactive and overactive thyroid?

An underactive thyroid (hypothyroidism) is where your thyroid gland is not making enough thyroid hormones. 

On the other hand, an overactive thyroid (hyperthyroidism) occurs when your thyroid makes too much of the thyroid hormones.  

These conditions have different effects and cause different symptoms. The difference between them may be easier to remember once you're aware that:

  • An underactive thyroid can cause weight gain and increased sensitivity to cold.

  • An overactive thyroid can cause weight loss and increased sensitivity to heat.

This, of course, is a very simplistic overview of their symptoms. For more information, you can click here for underactive thyroid symptoms and here for overactive thyroid symptoms. 

Both conditions can be treated with medication, and an overactive thyroid can also be treated with surgery or radioactive iodine treatment. 

How do I know if my thyroid is healthy?

The only way to know if your thyroid gland is functioning properly is to take a blood test. The Complete Blood Test is a home blood test that measures your thyroid hormones (TSH and free T4) to check how well your thyroid is working. 

It can also measure a variety of other important health indicators such as your testosterone levels, anaemia risk, and diabetes risk. This is especially useful if the reason you want to test your thyroid is because you have been experiencing fatigue (tiredness). Fatigue can also be caused by anaemia and diabetes, so it’s a good idea to test yourself for these and cover all the bases at once to be sure.