What is this test?
Free T3 is the active form of thyroid hormone in the body. It is ordered together with TSH and free T4, particularly when an overactive thyroid is suspected.
When is it requested?
Diagnosis and treatment monitoring of hyper- or hypothyroidism
What does a high free T3 result mean?
A high free T3 usually suggests an overactive thyroid (hyperthyroidism); in some people only T3 is raised. It is interpreted together with TSH and free T4.
- High-dose biotin supplements (falsely high result)
- Thyroid medication dose too high, especially T3-containing medicines
- Graves' disease
- An overactive thyroid nodule or nodular goiter
- Early phase of thyroid inflammation (thyroiditis)
What does a low free T3 result mean?
A low free T3 is often caused by non-thyroid factors such as illness or a low-calorie diet; on its own it is not a sign of hypothyroidism.
- Acute or chronic illness (non-thyroidal illness syndrome)
- Prolonged fasting or a very low-calorie diet
- Older age
- Certain medicines such as corticosteroids, beta-blockers or amiodarone
- Underactive thyroid (hypothyroidism), usually at a later stage
My result is outside the reference range. What should I do?
Free T3 is evaluated together with TSH and free T4, not alone. Pause biotin supplements before the test and tell your doctor about recent illness and your diet.
Reference ranges depend on the method, age and sex; always use the range printed on your report. This information is for general guidance only; consult your doctor for diagnosis and treatment.
Sample information
- Sample type: Serum
- Tube / container: Yellow-top tube
- Sample volume: 1 mL
Preparation
Fasting sample recommended.
Testing and results
- Method: ECLIA
- Run schedule: Daily
- Turnaround time: 4 hours
Price and appointment
Add the test to your list to receive a price quote by e-mail, or call +90 850 640 07 30 / message us on WhatsApp (+90 537 301 22 14). You can have the test done at our branches or with our home blood collection service. Results can be viewed online with your Turkish ID number (or passport number for foreign nationals).