total thyroxine test
total thyroxine (T4) test
a blood test that directly measures the total amount of T4 present in the patient's blood, with abnormal values indicating either hyperthyroid or hypothyroid states. This test is also used to monitor replacement suppressive therapy.
to·tal thy·rox·ine test(tōtăl thī-roksēn test)
A blood test to determine the circulating levels of thyroxine.