Thyroid hormone total triiodothyronine (T₃) concentration
This test measures the total amount of thyroid hormone triiodothyronine (T₃) in your blood. T₃ is one of the key hormones produced by your thyroid gland and plays a role in regulating metabolism, energy levels, and other bodily functions.
["Your doctor may check T₃ levels to assess thyroid function or diagnose conditions like hyperthyroidism or hypothyroidism."]
Key facts at a glance
- LOINC
- 47191-2
- Short code
- T3 sp2 p chal SerPl-sCnc
- Synonyms
- T3 sp2 p chal SerPl-sCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 80
- Ref high
- 200
- Critical range
- 20 N/A – 400 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 84436
- SNOMED
- 302346007
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why This Test Might Be Ordered
Your healthcare provider may recommend this test if you have symptoms such as unexplained weight changes, fatigue, anxiety, or irregular heart rhythms. It could also be part of a routine thyroid function panel or if you have a known thyroid disorder. Sometimes, doctors check T₃ levels alongside other thyroid tests, like thyroxine (T₄) or thyroid-stimulating hormone (TSH).
What to Expect Before the Test
No special preparation is usually needed for this blood test. You may be asked to fast for 8–12 hours before the draw, but always follow your provider’s instructions. Wear comfortable clothing and plan to stay near the testing site for a short time.
What Happens During the Test
A healthcare professional will insert a small needle into a vein in your arm to draw a blood sample. You may feel a slight pinch, but the process is quick. The blood is then sent to a lab for analysis. Most people experience minimal discomfort, though some may feel tired afterward.
What the Results Mean
Results help determine whether your thyroid is functioning normally or if there’s an imbalance. While reference ranges vary by lab, abnormal levels may signal thyroid issues, infections, or other health conditions. Your doctor will interpret the results in the context of your symptoms and medical history.
Reference range
Adult: 80-200 ng/dLN/A
Take your thyroid medication after the blood draw if applicable. No fasting required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Total T₃
Frequently asked questions
How often should I get this test?
What can affect my T₃ test results?
Do I need to take any special steps after the test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy