Thyroid Stimulating Hormone (TSH) with Immunoassay Method
This blood test measures the amount of thyroid-stimulating hormone (TSH) your body produces to regulate thyroid function.
["TSH helps diagnose thyroid issues like underactive (hypothyroidism) or overactive (hyperthyroidism) thyroid."]
Key facts at a glance
- LOINC
- 109055-4
- Short code
- TSH BII Msmt Ser
- Synonyms
- TSH BII Msmt Ser
- 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 check if your thyroid is working properly. It’s often the first test for thyroid problems, especially if you have symptoms like fatigue, weight changes, or unexplained mood swings. TSH levels can also help monitor thyroid treatment if you’ve been diagnosed with thyroid disease.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a larger panel. Wear comfortable clothing for the blood draw, and let your doctor or phlebotomist know about any medications you’re taking or medical conditions you have.
What Happens During the Test?
A small needle will be used to draw blood from a vein in your arm. The process takes just a few minutes, and you may feel a slight pinch. The blood sample is then sent to a lab for analysis using an immunoassay method to measure TSH levels accurately.
What Do Results Mean?
Results can vary based on your health, age, and other factors. High TSH levels may suggest hypothyroidism, while low levels could indicate hyperthyroidism or an underlying issue like a thyroid tumor. Your doctor will interpret results in the context of your symptoms and medical history.
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. Low TSH often signals hyperthyroidism (overactive thyroid), while high TSH typically points to hypothyroidism (underactive thyroid). It’s also useful for monitoring thyroid replacement therapy. Abnormal results may prompt further testing, such as free T4 or antibody checks, to pinpoint the cause.
Short name
TSH Level
Frequently asked questions
How long does it take to get my TSH test results?
Can I eat or drink before a TSH test?
What symptoms might indicate a need for 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