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T4 test



Blood test
Blood test


T4 test

Alternative Names:

Thyroxine test
Normal Values:

Normal values vary among different laboratories. A typical normal range is: 4.5 to 11.2 mcg/dL (micrograms per deciliter).


What abnormal results mean:

Greater-than-normal levels of T4 along with low levels of TSH may indicate hyperthyroid conditions, such as:

  • Graves' disease
  • toxic multinodular goiter
  • subacute or chronic thyroiditis
  • early Hashimoto's disease
  • iodine-induced hyperthyroidism
  • germ cell tumors
  • trophoblastic disease


Lower-than-normal levels of T4 may indicate:

  • hypothyroidism (including Hashimoto's disease, cretinism,myxedema, goitrous diseases, scleroderma, amyloid goiter, or hemochromatosis following neck irradiation for head and neck cancer)
  • malnutrition or fasting
  • illness throughout the body
  • use of certain prescribed medication, including dexamethasone, propranolol, lithium, iodine, methimazole, propylthiouracil, interferon alfa, interleukin-2, and amiodarone

Additional conditions under which the test may be performed:




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