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A Complete Guide On Thyroid Tests

If you have ever had the signs or symptoms of over or underactive thyroid glands, then the first thing your doctor might have recommended is to get a thyroid test done; but what is it? And more importantly, why is it necessary?

What Are Thyroid Tests?

Thyroid tests are used to measure TSH levels: the thyroid-simulating hormone, thyroxin (T4), and triiodothyronine (T3) in the blood. These are the thyroid hormones produced by the thyroid gland, a butterfly-shaped gland present in your neck at the lower frontal part. The thyroxin (T4) and triiodothyronine (T3) hormones are produced by the thyroid gland. 

What are the thyroid diseases diagnosed by a thyroid test?

The primary purpose of thyroid hormones in the human body is to regulate metabolism and metabolic activities. So the two major diseases diagnosed by a thyroid test are hyperthyroidism and hypothyroidism. 

Hyperthyroidism -  In this condition, the thyroid hormone produces an excess of the thyroid hormone, leading to increased metabolic activities, accelerated heart rates, enhanced sweating, unexpected weight loss, etc. 

Hypothyroidism - This is the exact opposite of the condition explained above. In this, the thyroid gland produces lower amounts of hormones. The deficiency leads to low metabolism, making the patient feel more tired, constipated, increased weight, dry skin, changes in temperatures, and altered heartbeats.

There can be pre-existing conditions that can affect the thyroid gland, which later leads to these diseases; the conditions are - 

  • Thyroiditis
  • Grave’s disease
  • Hashimoto’s disease
  • Goiter
  • Thyroid nodule
  • Thyroid cancer 

What is the procedure for the collection of a sample?

Similar to many tests, a thyroid test requires a sample of your blood collected through venipuncture. 

  1. First, the blood is taken using a sterilized needle.
  2. Next, the blood sample is collected in a sterilized test tube or vial; the latter is preferred for blood samples.

The blood sample is later given to the pathology for its analysis and the thyroid tests. Booking lab tests online is a good option for the test; the personnel come to your home, collect the blood sample, and give it to the pathology.

How To Understand The Test Results?

As explained earlier, thyroid tests determine the level of TSH, T3 & T4 in the blood; a high TSH level means that the thyroid gland is not producing enough hormones, which means that the person is diagnosed with hypothyroidism vice-versa. Usually, a thyroid test can take up to a day to produce the results.

TSH Levels 

  • Normal TSH Levels

The normal level of an average adult lies between 0.4 to 4.0 miU/L (milli-international units per liter). 

  • High TSH Levels 

Suppose the level of TSH is higher than the one given above. In that case, it determines that the thyroid gland is underactive, producing fewer hormones and thus, leading to hypothyroidism. Resulting in excess release of TSH by the pituitary gland in the blood.

  • Low TSH Levels 

A lower TSH level means that the gland is overactive and produces hormones in excess quantities, leading to hyperthyroidism, making the pituitary gland release less or almost no TSH into the blood. 

T4 Levels 

  • Normal T4 Level

The normal level of T4 for an adult lies between 0.8 to 2.8 nanograms per deciliter (ng/dL). 

  • High T4 Levels - 

If a high level of T4 in the bloodstream is recorded, it means that the patient has an underactive thyroid gland and is suffering from hypothyroidism.

  • Low T4 Levels - 

Low levels of T4 in the blood indicate that the thyroid gland is overactive and the patient is suffering from hyperthyroidism.


  1. Aman Verma says:

    A nice guide on a thyroid tests. It covers all the major things.

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