What are thyroid blood tests and why are they taken?

Thyroid blood tests are used to tell if your thyroid gland is functioning properly by measuring the amount of thyroid hormones in your blood. They are done by withdrawing blood from a vein in your arm. These blood tests help to diagnose thyroid diseases.

The thyroid is a butterfly-shaped gland located in the front part of your neck. Its job is to produce thyroid hormones, which travel through your bloodstream and regulate many aspects of your body’s metabolism, including temperature, weight, and energy.

Thyroid blood tests show if you have:

  • Hyperthyroidism: Overactive thyroid producing more thyroid hormones than your body needs. Hyperthyroidism speeds up your metabolism, which can cause weight loss, rapid heartbeat, insomnia, puffiness around the eyes, anxiety and other symptoms. The most common cause of hyperthyroidism is Graves’ disease.
  • Hypothyroidism: Underactive thyroid producing too few thyroid hormones. Hypothyroidism slows down your metabolism, which can cause weight gain, menstrual irregularity, dry and puffy skin, fatigue and other symptoms. The most common cause of hypothyroidism is Hashimoto’s disease.

Thyroid blood tests are used to diagnose thyroid disorders associated with hyper- or hypothyroidism. These include:

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