Thyroid Stimulating Hormone (TSH) with Confirmatory Immunoassay (Serum/Plasma)
This test measures your thyroid-stimulating hormone levels in your blood to help diagnose or monitor thyroid conditions, such as hypothyroidism or hyperthyroidism.
["A confirmatory TSH test helps ensure accurate results for thyroid function."]
Key facts at a glance
- LOINC
- 56594-5
- Short code
- TSH 3h p chal SerPl-aCnc
- Synonyms
- TSH 3h 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 This Test Is Done
Your healthcare provider may order this test if you have symptoms like fatigue, weight changes, or unexplained goiter (enlarged thyroid). It may also be used to monitor thyroid hormone treatment or screen for thyroid disorders in certain groups, such as pregnant women or those with family history of thyroid disease.
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 your blood is drawn early in the morning. Avoid smoking or caffeine for at least 30 minutes before your visit.
During the Test
A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but the process usually takes just a few minutes. The blood sample is then sent to a lab for analysis using an immunoassay method to detect TSH levels.
What the Results Mean
Results are interpreted by your healthcare provider based on your symptoms, medical history, and other tests. Abnormal results may prompt further evaluation, such as additional thyroid function tests or imaging.
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
Short name
Confirmatory TSH
Frequently asked questions
What does a high TSH level usually indicate?
What does a low TSH level usually indicate?
Why might my TSH test be repeated?
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