What this test is
The test measures unbound triiodothyronine in blood, which acts directly on target cells. A raised free T3 helps confirm hyperthyroidism, particularly when free T4 is inconclusive.
Category: Thyroid Function
Free T3
Free T3 is the most biologically active thyroid hormone. It is used to assess hyperthyroidism together with TSH and free T4.
What it is used for, and who should test
- Confirming hyperthyroidism when TSH and free T4 do not match symptoms
- Monitoring hyperthyroidism when a doctor wants T3 included
- Evaluating suspected T3 toxicosis, which occurs in some patients
Sample and preparation
- Sample
- 2-3 mL of blood in a serum tube
- Preparation
- No fasting required, but acute illness and prolonged fasting can lower T3 without thyroid disease.
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
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
Why is free T3 not always tested?
TSH and free T4 are sufficient for most diagnoses. Free T3 is added when those results do not match the clinical picture.
Does low free T3 mean an underactive thyroid?
Not necessarily. Severe illness, surgery or prolonged fasting can lower it, so doctors interpret it in context.
How should I prepare for Free T3?
No fasting required, but acute illness and prolonged fasting can lower T3 without thyroid disease.
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 T3 cost?
Prices are not shown on this website. Ask for pricing and packages on LINE @824xsgsj or call 063-223-6161.
Contact us
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
063-223-6161LINE 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