Thyroid-Stimulating Hormone (TSH) with Immunoassay Method
This blood test measures your thyroid-stimulating hormone level, which helps your body regulate metabolism and thyroid hormone production.
["TSH helps doctors check if your thyroid is working properly."]
Key facts at a glance
- LOINC
- 29575-8
- Short code
- TSH DBS-aCnc
- Synonyms
- TSH DBS-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
Your doctor may order a TSH test to diagnose or monitor thyroid conditions, such as hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid). It’s also used during pregnancy, to check for thyroid issues before surgery, or to evaluate symptoms like fatigue, weight changes, or unexplained goiter.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the blood draw if your test is part of a more complex evaluation. Wear comfortable clothing and plan for the test to take about 15 minutes. Avoid smoking or caffeine before the draw if instructed.
What Happens During the Test
A healthcare provider will insert a small needle into a vein in your arm to draw blood. You may feel a slight pinch, but it usually doesn’t cause discomfort. The blood sample is sent to a lab for analysis using an immunoassay method to measure TSH levels.
What the Results Mean
Results are interpreted based on your symptoms, medical history, and other tests. Low TSH levels may suggest hyperthyroidism, while high levels may indicate hypothyroidism. Your doctor will discuss findings with you and may recommend follow-up tests or treatments.
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 thyroid disorders that may affect energy levels, digestion, heart function, and mood. Early detection helps manage conditions like Hashimoto’s disease or Graves’ disease, which can improve long-term health outcomes.
Short name
TSH
Frequently asked questions
What causes TSH levels to be too high or too low?
Can diet or lifestyle affect TSH test results?
How often should I get 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