Thyroid Stimulating Hormone (TSH) with Serum Specimen
This blood test measures your thyroid-stimulating hormone, a key hormone that helps regulate your metabolism and energy levels by signaling your thyroid gland to produce thyroid hormones.
["Your TSH level helps doctors check if your thyroid is working properly."]
Key facts at a glance
- LOINC
- 50538-8
- Short code
- TSH sp6 SerPl-aCnc
- Synonyms
- TSH sp6 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
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 used to check thyroid function, especially if you have symptoms like fatigue, weight changes, or sensitivity to heat/cold.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a metabolic panel. Bring any medications you’re currently taking, as some (like thyroid hormone replacement) can affect results.
What the Test Results Mean
Results are interpreted based on your symptoms and overall health. Low TSH levels may suggest hyperthyroidism, while high levels may indicate hypothyroidism. Your doctor will discuss findings in relation to your specific situation.
Common Conditions Linked to Abnormal TSH
Elevated TSH is often linked to hypothyroidism, a condition where your thyroid doesn’t produce enough hormones. Low TSH can signal hyperthyroidism, where the thyroid produces too much. Other causes may include thyroid nodules, pituitary disorders, or thyroiditis (inflammation).
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 screening tool for thyroid disorders, as it’s highly sensitive and specific for detecting imbalances. It’s also useful for monitoring thyroid replacement therapy or managing thyroid-related conditions over time.
Short name
TSH Level
Frequently asked questions
What does a ‘normal’ TSH level mean for me?
Can diet or medications affect my 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