Thyroid hormone total serum triiodothyronine (T₃) concentration
This test measures the total amount of the 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.
["Assessing your thyroid function and overall metabolic health."]
Key facts at a glance
- LOINC
- 47196-1
- Short code
- T3 sp7 p chal SerPl-sCnc
- Synonyms
- T3 sp7 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 like fatigue, weight changes, or irregular heartbeats, or if they suspect thyroid dysfunction. It may also be part of a routine check-up or follow-up for conditions like hypothyroidism or hyperthyroidism.
What to Expect Before the Test
No special preparation is needed for this blood test. You may have fasting instructions depending on your other tests, so always follow your provider’s guidance. Bring any medications you’re currently taking.
What the Test Involves
A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause significant discomfort. The process takes about 5 minutes.
What the Results Mean
Results help determine if your thyroid hormone levels are within a healthy range. Abnormal levels may indicate thyroid issues, but interpretation depends on your overall health and other tests.
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.
Thyroid hormones like T₃ are essential for maintaining energy levels, metabolism, and brain function. Low levels may cause fatigue, weight gain, or depression, while high levels could lead to anxiety, rapid heartbeat, or muscle weakness. This test is often used alongside other thyroid tests (like TSH) to diagnose or monitor thyroid disorders.
Short name
T₃ Total Serum
Frequently asked questions
How long does it take to get my results?
What does a low or high T₃ level mean?
Can I take anything before or 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