Thyroid Stimulating Hormone (TSH) with Serum/Plasma Specimen, Immunoassay Method
This test measures your thyroid-stimulating hormone, a key hormone your body uses to regulate thyroid function. It helps assess whether your thyroid is working properly.
["Your TSH level helps determine if your thyroid is underactive, overactive, or functioning normally."]
Key facts at a glance
- LOINC
- 12942-9
- Short code
- TSH sp3 p chal SerPl-aCnc
- Synonyms
- TSH sp3 p chal SerPl-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0.4
- Ref high
- 4
- Critical range
- 0.1 N/A – 20 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 84443
- SNOMED
- 301343003
- 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 Is Done
Doctors order TSH tests to check for thyroid disorders, such as hypothyroidism (low thyroid activity) or hyperthyroidism (overactive thyroid). It may also be used during pregnancy, before surgery, or when managing conditions like diabetes or heart disease.
How the Test Works
A small blood sample is taken from a vein in your arm. The sample is sent to a lab where it is analyzed using an immunoassay to detect and measure TSH levels.
What to Expect Before the Test
No special preparation is needed for this test. However, you may be asked to fast for 8–12 hours before the test if your doctor recommends it, though this is not always required for TSH.
What the Results Mean
Results are interpreted by your healthcare provider based on your symptoms, medical history, and other tests. High TSH levels often indicate hypothyroidism, while low levels may suggest hyperthyroidism or other conditions.
Reference range
Adult: 0.4-4.0 mIU/LN/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.
TSH is the primary hormone used to monitor thyroid function. Abnormal levels can signal thyroid disorders that may require treatment, such as medication adjustments, hormone replacement, or further diagnostic testing. It is also a critical marker in conditions like pituitary disorders or thyroid cancer.
Short name
TSH Level
Frequently asked questions
How long does it take to get my TSH test results?
Can I eat or drink before this test?
What are common reasons doctors order a TSH 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 16, 2026. · Read our editorial policy