Thyroid Function Test (TFT) – Details & Precautions

The Thyroid Function Test (TFT) is a blood test that measures hormone levels to assess thyroid gland function. It helps diagnose thyroid disorders such as hypothyroidism, hyperthyroidism, and autoimmune thyroid diseases.

---

Details of the TFT Test

Purpose

• Diagnoses hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid).
• Monitors thyroid disorders and hormone therapy.
• Detects autoimmune thyroid diseases like Hashimoto’s thyroiditis and Graves’ disease.
• Evaluates thyroid function in pregnancy.

Test Components

• Thyroid-Stimulating Hormone (TSH) – Regulates thyroid hormone production.
• Free T3 (Triiodothyronine) – Active thyroid hormone that controls metabolism.
• Free T4 (Thyroxine) – Precursor hormone to T3.
• Total T3 & Total T4 – Measures both bound and free thyroid hormones.
• Thyroid Antibodies (TPO, TG, TRAb) – Detects autoimmune thyroid diseases.

Test Method

• A blood sample is drawn from a vein in the arm and analyzed in a laboratory.

---

Precautions for the TFT Test

Before the Test

✅ Fasting:

• Fasting is usually NOT required, but some doctors may recommend 8–12 hours of fasting for more accurate results.

✅ Medication Restrictions:

• Avoid thyroid medications (like levothyroxine) before the test, as advised by your doctor.
• Inform your doctor about steroids, birth control pills, antacids, iodine supplements, and biotin, as they may interfere with results.

✅ Avoid Biotin Supplements:

• Stop taking biotin (Vitamin B7) at least 48 hours before the test, as it can interfere with thyroid hormone measurements.

✅ Avoid Alcohol & Caffeine:

• Avoid alcohol and caffeine for 24 hours before the test, as they can impact thyroid hormone levels.

✅ Time of Test:

• TFTs are usually done in the morning, as TSH levels fluctuate throughout the day.

During the Test

• A small blood sample is taken from a vein; mild pain or bruising may occur at the injection site.

After the Test

✅ Resume normal activities immediately.
✅ If fasting, eat a balanced meal after the test.
✅ Follow up with your doctor if results indicate thyroid dysfunction.