Thyroxine - Free (FT4) Test

Also referred as

Free T4

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The Thyroxine - Free (FT4) Test test measures the amount of free form of thyroxine hormone in the blood. This test helps evaluate the functioning of the thyroid gland and detect possible thyroid disorders. It is also performed in combination with free T3 and TSH tests as part of a thyroid profile free test.

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Understanding Thyroxine - Free (FT4) Test

Thyroxine or T4 is a thyroid hormone that regulates your body’s metabolism, temperature, blood pressure, heart rate, etc. It is produced along with the T3 hormone and plays an important role in the growth and development of the nervous system and the brain. T4 hormone exists in the blood in two forms: bound (attached to proteins) and free (not attached to proteins). Deranged levels of this hormone can result in either hyperthyroidism (the thyroid gland produces too much T4) or hypothyroidism (the thyroid gland produces less T4).

The Thyroxine - Free (FT4) Test test measures the amount of free thyroxine hormone (T4), which is not attached to any protein. Your doctor may suggest this test if you show symptoms suggestive of hyperthyroidism, like increased appetite, weight loss, sweating, anxiety, tremors, etc., or hypothyroidism, like fatigue, weight gain, dry skin, constipation, etc.

No special preparations are needed for this test. Usually, you do not need to stop taking your thyroid medication before taking this test. However, do let your doctor know about all the medications you take as some of them can affect your thyroid test results. Biotin (Vitamin B7) is a commonly taken over-the-counter supplement that can lead to some aberrancy in your thyroid function tests even when the values are actually normal. Hence, avoid taking biotin 2 days before this test.

Test result ranges are approximate and may differ slightly between different labs depending on the methodology and laboratory guidelines. Talk to your doctor about your specific results. The test results will help them determine your medical condition, make recommendations for lifestyle modifications such as diet and exercise, evaluate whether or not medication will be required to manage your condition, and formulate an overall treatment plan.

What does Thyroxine - Free (FT4) Test measure?

The Thyroxine - Free (FT4) Test test measures the free form of thyroxine (T4) hormone made by the thyroid gland. T4 hormone exists in the blood in two forms: bound (attached to proteins) and free (not attached to proteins). Most of the T4 hormone circulating in the blood is bound to proteins and only a small part is free. A delicate balance of bound and free T4 should be maintained to ensure the proper functioning of the body.

Packages containing Thyroxine - Free (FT4) Test

Comprehensive Platinum Package with ECG, USG Whole Abdomen & 2D-Echo

Contains 102 tests

Get reports within 12-15 hrs

₹6666

Comprehensive Platinum Full Body Checkup with Smart Report

Contains 100 tests

Get reports within 18-24 hrs

₹3999

Fitness Advanced Package for Women with Smart Report

Contains 89 tests

Get reports within 36-48 hrs

₹3999

Fitness Advanced Package for Men with Smart Report

Contains 88 tests

Get reports within 36-48 hrs

₹3999

Men Advanced Plus Health Checkup with Smart Report

Contains 99 tests

Get reports within 12-24 hrs

₹3559

Women Advanced Plus Health Checkup with Smart Report

Contains 81 tests

Get reports within 18-24 hrs

₹3589

PMOS (formerly PCOS) Advanced Package

Contains 26 tests

Get reports within 36-48 hrs

₹3399

Senior Citizen Women Advanced Health Checkup with Smart Report

Contains 101 tests

Get reports within 18-24 hrs

₹4149

Senior Citizen Men Advanced Health Checkup with Smart Report

Contains 103 tests

Get reports within 18-24 hrs

₹4299

Comprehensive Diamond Full Body Checkup with Smart Report

Contains 104 tests

Get reports within 15-24 hrs

₹4999

Frequently booked together

TSH (Thyroid Stimulating Hormone) Ultrasensitive Test

Also known as Thyrotropin, Thyrotropic hormone

Report in 7 hrs

₹369

~~₹419~~

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CBC (Complete Blood Count)

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~~₹389~~

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PPBS (Postprandial Blood Sugar) Test

Also known as Postprandial plasma glucose concentration, Sugar PP, 2-hour postprandial, Glucose Postprandial (PP)

Report in 7 hrs

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~~₹179~~

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Triiodothyronine - Free (FT3) Test

Also known as T3 - Free

~~₹380~~

Also known as Lipid panel, Cholesterol profile, Fasting lipid profile

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Thyroid Profile Total (T3, T4 & TSH)

Also known as Thyroid Panel, TFT, Thyroid Function Test

Report in 7 hrs

₹539

~~₹609~~

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Test Information is reviewed by: Dr. Anupriya Nautiyal, MD Pathology, MBBS and written by Shweta Prakash, MSc, BSc . The test details are for information purpose only. Consult a doctor before taking any test. Last updated on: 12th Nov 2026

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Thyroxine - Free (FT4) Test test price for other cities

Price in	Kolkata	Rs. 339
Price in	Bangalore	Rs. 329
Price in	New Delhi	Rs. 339
Price in	Dehradun	Rs. 230
Price in	Hyderabad	Rs. 200

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FAQs related to Thyroxine - Free (FT4) Test

Why is the Thyroxine - Free (FT4) Test test done?

The Thyroxine - Free (FT4) Test test is done to evaluate symptoms of hypothyroidism (weight gain, fatigue, dry skin, hair thinning, slow heart rate, or depression) and hyperthyroidism (weight loss, muscle weakness, anxiety, trouble sleeping, tremors, or frequent bowel movement).

Can I take the Thyroxine - Free (FT4) Test test during pregnancy?

Yes, you can take the free T4 test during pregnancy. This test along with others is usually recommended during pregnancy to measure the levels of thyroid hormones, as thyroid disorders can complicate pregnancy.

What do high T4 levels signify?

High T4 levels can lead to a condition called hyperthyroidism in which the thyroid gland produces too much thyroid hormone. Some of the common causes of hyperthyroidism include nodular goiter and thyroiditis.

What happens when the T4 level is low?

Low T4 levels can lead to a condition called hypothyroidism. Some of the common symptoms of hypothyroidism are fatigue and weakness, weight gain, cold intolerance, and constipation.

How can I reduce my T4 levels naturally?

Always consult your doctor if your test results show high levels of T4 hormone. However, some home remedies, including apple cider vinegar, ginger, vitamin B (fish, legumes, milk, and nuts), vitamin D, dairy products, regular exercise, etc., might help you to lower your T4 levels naturally.

Is fasting required for the Free T4 test?

No, fasting is not needed before taking this test. However, your doctor will guide you if any special preparation is required.

What factors can affect the test results of the Free T4 test?

Certain medications like phenobarbital, amiodarone, or diclofenac can have an impact on your free T4 levels. Besides these, severe cases of chronic ailments, such as liver cirrhosis or chronic kidney failure, can also affect the results of the Free T4 test.

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