Thyroid Stimulating Hormone (TSH) with Serum/plasma Measurement
This test measures the level of thyroid-stimulating hormone in your blood, which helps regulate your thyroid function.
["TSH helps your thyroid produce hormones that control metabolism and energy levels."]
Key facts at a glance
- LOINC
- 12929-6
- Short code
- T4 sp8 p chal SerPl-mCnc
- Synonyms
- T4 sp8 p chal SerPl-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 4.5
- Ref high
- 12
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 84436
- SNOMED
- 302345006
- 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
What Is TSH Used For?
TSH is primarily used to diagnose and monitor thyroid disorders, such as hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid). It can also help determine if thyroid hormone replacement therapy is working properly.
How Is the Test Performed?
A blood sample is taken from a vein, usually in your arm, and sent to a lab for analysis. The test measures the amount of TSH in your serum or plasma.
What Are Common Results and Their Implications?
Elevated TSH levels may suggest hypothyroidism, while very low levels could indicate hyperthyroidism or other conditions affecting thyroid function. Your doctor will interpret results in the context of your symptoms and medical history.
Why Might I Need This Test?
Your doctor may order a TSH test if you have symptoms like fatigue, weight changes, or unexplained issues with metabolism. It’s also commonly checked during pregnancy, before starting thyroid hormone treatment, or as part of routine health screenings.
Reference range
Adult: 4.5-12.0 μg/dLN/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.
◆Associated findings1
Short name
TSH (Serum/Plasma)
Frequently asked questions
TSH is a critical hormone produced by the pituitary gland to regulate thyroid hormone production. Abnormal levels can signal thyroid dysfunction, which may require medical evaluation, treatment adjustments, or further testing (e.g., free T4 or antibody checks).
A normal TSH level doesn’t necessarily mean your thyroid is functioning perfectly—it’s a starting point. Your doctor will assess whether your results align with your symptoms and overall health before making a diagnosis.
Yes, factors like stress, sleep, diet, and certain medications can influence TSH levels. Avoiding caffeine or thyroid medications for a few days before testing may help get a more accurate result.
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