Free Thyroxine (FT4)

Free thyroxine (FT4) is one of the main hormones produced by the thyroid gland, and measuring the unbound, active fraction helps assess how the thyroid is functioning. It is a standard part of thyroid testing, often alongside TSH and FT3, when investigating tiredness, weight change or other thyroid-related symptoms. At Centrum Medyczne Medix it is run in the on-site laboratory at a fixed published price.

Free thyroxine (FT4) is the active, unbound form of thyroxine, the principal hormone secreted by the thyroid gland to help regulate metabolism. Measuring the free fraction — rather than the total, much of which is bound to proteins — gives a clearer indication of how much hormone is actually available to the body's tissues, which is why FT4 is a core component of thyroid assessment. FT4 is usually interpreted together with other thyroid markers, particularly TSH (the pituitary signal that drives the thyroid) and sometimes FT3, to build a picture of whether the gland is underactive, overactive or working normally. Patterns in these results are associated with conditions a doctor will interpret in context, and the panel is commonly requested when symptoms such as fatigue, unexplained weight change, temperature sensitivity, mood changes or palpitations are being investigated, as well as to monitor people on thyroid medication. The test uses a standard venous sample and generally needs no special preparation, though anyone on thyroid treatment should follow their doctor's advice on timing. At Centrum Medyczne Medix the measurement is processed in the centre's own laboratory at a transparent listed price, and complementary markers such as FT3 and anti-TPO antibodies are also available from the same price list. The laboratory is open Monday to Friday 8:00–19:00 and Saturday 8:00–13:00, and an endocrinologist can be seen at the centre if follow-up is required.