Thyroid hormone total triiodothyronine (T3) concentration in serum/plasma
This test measures the total amount of the hormone triiodothyronine (T3) in your blood. T3 is a key thyroid hormone that helps regulate metabolism, energy levels, and other bodily functions.
["T3 helps control your metabolism and energy levels, and low or high levels may signal thyroid issues."]
Key facts at a glance
- LOINC
- 47195-3
- Short code
- T3 sp6 p chal SerPl-sCnc
- Synonyms
- T3 sp6 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 order this test to evaluate thyroid function, especially if you have symptoms like fatigue, weight changes, or unexplained heart issues. It can also be used to monitor thyroid hormone levels during treatment for conditions like hypothyroidism or hyperthyroidism.
What to Expect Before the Test
No special preparation is typically needed for this test. You may have a blood sample drawn from a vein in your arm, similar to other blood tests. If you’re on thyroid medication, let your provider know before the test.
What the Results Mean
Results help determine whether your thyroid is functioning normally. Abnormal levels might suggest thyroid disorders, but they’re not definitive on their own. Your provider will interpret results in the context of your symptoms and other tests.
Common Reasons for Abnormal Results
Low T3 levels can occur with hypothyroidism (underactive thyroid), stress, or certain medications. High T3 levels may indicate hyperthyroidism (overactive thyroid), thyroid nodules, or other metabolic conditions. Always discuss results with your doctor.
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
T3 Total
Frequently asked questions
How often is this test repeated?
What does it feel like to have abnormal T3 levels?
Can diet affect T3 test results?
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