Thyroid Stimulating Hormone (TSH) with Serum Specimen
This test measures the amount of thyroid-stimulating hormone (TSH) in your blood, which helps your thyroid gland produce hormones that regulate metabolism.
["TSH helps diagnose thyroid issues and guides treatment for conditions like hypothyroidism or hyperthyroidism."]
Key facts at a glance
- LOINC
- 3016-3
- Short code
- TSH SerPl-aCnc
- Synonyms
- TSH 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 Is This Test Done?
Your doctor may order a TSH test to check for thyroid problems, such as whether your thyroid is working too slowly (hypothyroidism) or too quickly (hyperthyroidism). It’s often the first test used to evaluate thyroid function, especially if you have symptoms like fatigue, weight changes, or unexplained mood swings.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if your blood is drawn early in the morning. Bring any medications you’re taking, as some (like certain thyroid medications) can affect results.
How the Test Works
A small blood sample is taken from a vein in your arm. The blood is sent to a lab where it’s analyzed to measure TSH levels using an immunoassay method. This test detects the hormone produced by your pituitary gland to signal your thyroid to produce hormones.
What the Results Mean
Results can vary based on your health and lab standards. High TSH levels may suggest hypothyroidism, while low levels may indicate hyperthyroidism. Your doctor will interpret results in relation to your symptoms and medical history.
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 a critical marker for thyroid function. Abnormal levels can signal underlying conditions like Hashimoto’s thyroiditis (autoimmune hypothyroidism), Graves’ disease (hyperthyroidism), or thyroid nodules. It’s also useful for monitoring thyroid replacement therapy in patients with hypothyroidism.
Short name
TSH Level
Frequently asked questions
What causes TSH levels to be abnormal?
How long does it take to get TSH test results?
Can lifestyle changes affect TSH 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 16, 2026. · Read our editorial policy