Also Known As: Thyroxine (T4) and triiodothyronine (T3)

Consult for FT4 at Samyak.

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About the Test

T4 is made by the thyroid gland and converted to T3 by the liver. These hormones control energy production (metabolic rate) in tissues.

Clinical Significance:

As follow up to an abnormal TSH test. Laboratory tests may measure either the total hormone or free hormone (not bound to protein)

More about Tests

Learn more about laboratory testing

Target Levels (where applicable)


REFERENCE INTERVALS FOR ADULTS: FT3: 1.71-3.71 pg/ml FT4: 0.70-1.48 ng/dl.

What is being checked


INCREASE IN: Hyperthyroidism

DECREASE IN: Hypothyroidism