What sample is required?
The determination is made from a venous blood sample.
Is some kind of prior preparation necessary?
For this test you do not need any special preparation.
Why do the analysis?
To assess the function of the thyroid gland; to diagnose hypothyroidism or hyperthyroidism; for screening newborns for hypothyroidism.
When to do the analysis?
Usually in response to an abnormal TSH test or when a person has symptoms of hyperthyroidism or hypothyroidism; routinely performed on newborns.