Thyroid Stimulating Hormone (TSH) with Serum/Plasma Measurement by Immunoassay
This test measures the amount of thyroid-stimulating hormone (TSH) in your blood. TSH helps regulate your thyroid hormone levels, which control metabolism, energy, and overall health.
["TSH helps doctors check if your thyroid is working properly."]
Key facts at a glance
- LOINC
- 12935-3
- Short code
- TSH 20M p chal SerPl-aCnc
- Synonyms
- TSH 20M 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 Is This Test 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 often the first test for thyroid issues because it’s sensitive and easy to measure.
What to Expect Before the Test
No special preparation is usually needed. You may have a small needle inserted into your arm or hand to draw blood. If you’re on thyroid medication, let your doctor know before the test.
What the Results Mean
TSH results help determine whether your thyroid is producing too much or too little hormone. High TSH levels often suggest hypothyroidism, while very low levels may indicate hyperthyroidism. Your doctor will interpret results in relation to your symptoms and medical history.
Common Conditions This Test Helps Diagnose
This test is commonly used to diagnose or manage thyroid disorders, including Hashimoto’s disease (autoimmune hypothyroidism), Graves’ disease (hyperthyroidism), and thyroid nodules. It can also help monitor treatment progress for thyroid 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.
Clinical Significance: TSH is a key marker for thyroid function. Abnormal levels can signal underlying thyroid disorders that may require treatment, such as hormone replacement therapy or medication adjustments. Regular monitoring with TSH testing is important for patients with thyroid conditions or those at risk for thyroid disease.
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?
Will this test show if I have other health conditions besides thyroid issues?
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