Thyroid Hormone Tests

T3 (Triiodothyronine) Test, T4 (Thyroxine) Test, Thyroxine (T4) Test, Triiodothyronine (T3) Test

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Taking certain medicines, such as:
  • Corticosteroids, estrogen, progesterone, or birth control pills.
  • Blood-thinning medicines such as aspirin, heparin, or warfarin (Coumadin).
  • Antiseizure medicines such as Dilantin or Tegretol.
  • Heart medicines such as amiodarone or propranolol.
  • Lithium.
• Having recently had an X-ray test that uses contrast material.
• Being pregnant.

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Author:	Caroline Rea, RN, BS, MS	Last Updated: December 3, 2007
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine David C.W. Lau, MD, PhD, FRCPC - Endocrinology & Metabolism
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