Thyroid Stimulating Hormone (TSH) with Serum/Plasma Measurement
This test measures the amount of thyroid-stimulating hormone in your blood, which helps regulate your thyroid function.
["Your TSH level helps doctors check if your thyroid is working properly."]
Key facts at a glance
- LOINC
- 12937-9
- Short code
- TSH 45M p chal SerPl-aCnc
- Synonyms
- TSH 45M 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
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’s often the first test recommended if you have symptoms like fatigue, weight changes, or unexplained mood swings.
How Is the Test Performed?
A small blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where it is analyzed using an immunoassay method to measure TSH levels.
What Might Affect Your Results?
Several factors can influence TSH levels, including medications (like thyroid hormone replacement or certain antidepressants), pregnancy, stress, and underlying health conditions. If you’re taking medications or have recent changes in health, let your healthcare provider know.
Common Symptoms Linked to Abnormal TSH Levels
High TSH levels may suggest hypothyroidism, causing symptoms like cold intolerance, dry skin, or weight gain. Low TSH levels might indicate hyperthyroidism, leading to symptoms such as anxiety, rapid heartbeat, or unintended weight loss.
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 key marker for thyroid function because it signals the thyroid gland to produce thyroid hormones. Abnormal TSH levels can indicate imbalances that require medical attention, such as thyroiditis, pituitary disorders, or autoimmune conditions like Hashimoto’s disease.
Short name
TSH Level
Frequently asked questions
Why did my TSH test result come back different from what I expected?
No special preparation is usually needed, but avoid smoking or drinking alcohol before the test if advised by your doctor. If you’re taking thyroid medication, check with your provider first.
If your TSH test result is outside the normal range, your doctor may recommend further testing, such as checking free T4 or other thyroid-related markers, to determine the cause and guide treatment.
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