Thyroid-stimulating hormone (TSH) with serum/plasma measurement by immunoassay
This test measures the amount of thyroid-stimulating hormone (TSH) in your blood. TSH is a hormone produced by your pituitary gland that helps regulate your thyroid function.
["TSH helps your thyroid produce hormones that control metabolism."]
Key facts at a glance
- LOINC
- 47948-5
- Short code
- TSH 15M p LRH IV SerPl-aCnc
- Synonyms
- TSH 15M p LRH IV 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 healthcare provider may order this test to check for thyroid problems, such as hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid). It can also be used to monitor thyroid function during treatment for thyroid disorders or after thyroid surgery.
What Does a TSH Test Measure?
TSH levels help determine whether your thyroid is working too slowly or too quickly. High TSH levels often suggest hypothyroidism, while low TSH levels may indicate hyperthyroidism or other conditions affecting the pituitary or thyroid.
How Is the Test Performed?
A blood sample is taken from a vein, usually in your arm. The blood is sent to a lab where it is analyzed to measure TSH levels using an immunoassay method.
What Are Common Results and Their Meanings?
Results can vary based on individual health, age, and other factors. High TSH levels may signal hypothyroidism, while very low levels may suggest hyperthyroidism or conditions like pituitary tumors. Your results will be interpreted by your healthcare provider in the context of your overall health.
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.
Clinical Significance: TSH plays a critical role in thyroid hormone regulation. Abnormal TSH levels can indicate underlying thyroid dysfunction, which may require further evaluation or treatment to manage symptoms like fatigue, weight changes, or mood issues.
Short name
TSH (Serum/Plasma)
Frequently asked questions
What causes abnormal TSH levels?
How long does it take to get results?
Can diet or supplements 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