Category: Thyroid Function

Free T4

Free T4 is the unbound, immediately active thyroid hormone. It is used with TSH to confirm an underactive or overactive thyroid.

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What this test is

The test measures free thyroxine in blood, which is not bound to carrier proteins and therefore reflects the hormone available to tissues. Low free T4 with high TSH suggests hypothyroidism; high free T4 with low TSH suggests hyperthyroidism.

What it is used for, and who should test

Confirming abnormal TSH results or suspected thyroid disease from symptoms
Monitoring treatment of hyperthyroidism and hypothyroidism
Assessing pregnancy, where carrier proteins change and total hormone tests can mislead

Sample and preparation

Sample: 2-3 mL of blood in a serum tube
Preparation: No fasting required. Testing with TSH gives the fullest picture; mention your regular medicines.

Where to get tested

Samples are collected and results issued at S.F. Laboratory, the in-house laboratory of BK5 Med Health Clinic in Don Hua Lo, Chon Buri. No appointment is needed; walk in during opening hours.

Sample collection at BK5 Clinic, 149/6-7 Don Hua Lo, Chon Buri District, Chon Buri 20000
Open Monday-Friday 08.30-20.00 and Saturday 08.30-17.00
Ask questions or book ahead on LINE @824xsgsj or call 063-223-6161

063-223-6161 Get directions (Google Maps)

The information on this page is general knowledge to support your decisions and is not personal medical advice. Interpreting results and planning treatment requires assessment by a doctor. Please consult our medical staff before deciding on testing or treatment.

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Thyroid Function

Frequently asked questions about this test

How does free T4 differ from total T4?

Free T4 is the unbound active fraction, whereas total T4 includes hormone bound to carrier proteins and is more affected by pregnancy and certain medicines.

What if free T4 is normal but TSH is abnormal?

This may indicate early thyroid disease or a medicine effect. Doctors often repeat the test and review symptoms before deciding on treatment.

How should I prepare for Free T4?

No fasting required. Testing with TSH gives the fullest picture; mention your regular medicines.

How long do results take?

About 1 day, depending on the laboratory workload that day. Our staff will confirm the collection time when you are served.

Where can I have this test done?

Samples are collected and results issued at S.F. Laboratory, the in-house laboratory of BK5 Med Health Clinic in Don Hua Lo, Chon Buri. No appointment is needed; walk in during opening hours.

How much does Free T4 cost?

Prices are not shown on this website. Ask for pricing and packages on LINE @824xsgsj or call 063-223-6161.

Book a visit or ask a question

Add us on LINE @824xsgsj to ask about tests and pricing, or fill in the form below and our team will get back to you as soon as possible.

Phone

063-223-6161

LINE Official

@824xsgsj

Address

149/6-7 Don Hua Lo, Chon Buri District, Chon Buri 20000, Thailand

Get directions (Google Maps)

Opening hours

Monday - Friday: 08.30 - 20.00
Saturday: 08.30 - 17.00