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T3, Free
Access Labcorp Draw · Access Medical Labs · Quest Diagnostics3 test optionsFrom $12.16
T3, Free
Access Labcorp Draw · Access Medical Labs · Quest DiagnosticsCatalog information reviewed: August 24, 2026 by the Sunridge Medical clinical team.
What this laboratory test evaluates
DetailsThe Free T3 (FT3) test measures the level of triiodothyronine (T3) in the blood that is not attached to proteins. This test is important for diagnosing and managing hyperthyroidism and understanding thyroid health, especially when there might be issues with thyroid hormone-binding proteins. It's often used together with tests for thyroid-stimulating hormone (TSH) and free T4 (FT4) to get a full picture of thyroid function.
What patients is this test right for?This test is typically ordered if you have symptoms of hyperthyroidism or if other thyroid test results, like TSH or FT4, are unusual. Symptoms of hyperthyroidism include:
• Weight loss
• Rapid heartbeat
• Nervousness or irritability
• Sweating more than usual
• Feeling hot
• Changes in menstrual patterns
What type of sample is required for this test?1 mL serum. A blood draw is needed.
Additional test information
This test is typically ordered if patients exhibit symptoms of hyperthyroidism or if other thyroid test results, like TSH or FT4, are unusual.
Collection and processing
- Sample type: Serum
- Fasting: No
- Estimated laboratory processing: Results should be available in 2 – 5 business days after the sample is collected
How Sunridge uses laboratory information
Sunridge considers the medical question, symptoms, history, medications, prior results, and whether the finding could change care before recommending testing. A laboratory result is not interpreted in isolation and does not establish a diagnosis by itself.
Before requesting this test
Availability, collection requirements, eligibility, and processing estimates can change. Sunridge reviews each request and, when appropriate, creates the order through Fullscript. Follow the current instructions supplied with the approved order.
Common questions about this laboratory test
- What sample does this test require?
- The listed sample type is Serum. Confirm current collection instructions in the approved order.
- Does this test require fasting?
- The current catalog record lists fasting as: No. Follow the instructions supplied with the approved order.
- How long does laboratory processing usually take?
- Results should be available in 2 – 5 business days after the sample is collected. Timing can change after collection or if a laboratory requires additional review.
About this test
DetailsThe Free T3 (FT3) test measures the level of triiodothyronine (T3) in the blood that is not attached to proteins. This test is important for diagnosing and managing hyperthyroidism and understanding thyroid health, especially when there might be issues with thyroid hormone-binding proteins. It's often used together with tests for thyroid-stimulating hormone (TSH) and free T4 (FT4) to get a full picture of thyroid function.
What patients is this test right for?This test is typically ordered if you have symptoms of hyperthyroidism or if other thyroid test results, like TSH or FT4, are unusual. Symptoms of hyperthyroidism include:
• Weight loss
• Rapid heartbeat
• Nervousness or irritability
• Sweating more than usual
• Feeling hot
• Changes in menstrual patterns
What type of sample is required for this test?1 mL serum. A blood draw is needed.
Additional details
This test is typically ordered if patients exhibit symptoms of hyperthyroidism or if other thyroid test results, like TSH or FT4, are unusual.
Highlighted health areas
- Hormones
- Thyroid
Biomarkers and report focus
The exact analytes and report format can change. Confirm the current contents in the Fullscript order before payment.
- Free T3