TSH (Ultrasensitive)
What Is This Test?
The TSH (Ultrasensitive) test is a blood test that measures the level of Thyroid Stimulating Hormone (TSH) in the bloodstream. TSH is produced by the pituitary gland and regulates the production of thyroid hormones (T3 and T4) by the thyroid gland.
The ultrasensitive TSH assay can detect even very small changes in TSH levels, making it the preferred first-line test for evaluating thyroid function. It helps diagnose hypothyroidism (underactive thyroid), hyperthyroidism (overactive thyroid), monitor thyroid treatment, and assess thyroid health during pregnancy.
Why this test is performed?
Doctors may recommend the TSH (Ultrasensitive) test to:
- Diagnose hypothyroidism
- Diagnose hyperthyroidism
- Screen for thyroid disorders
- Monitor thyroid hormone replacement therapy
- Monitor treatment for hyperthyroidism
- Evaluate thyroid function during pregnancy
- Investigate unexplained weight changes
- Assess infertility or menstrual irregularities
- Evaluate thyroid nodules or goiter
- Monitor patients after thyroid surgery or radioactive iodine treatment
Test Preparation
No fasting is usually required.
Drink water normally unless instructed otherwise.
Inform your healthcare provider about any thyroid medications, iodine-containing supplements, or other medicines.
Biotin (Vitamin B7) supplements can interfere with thyroid test results. If you take high-dose biotin, your doctor may advise stopping it 24–72 hours before the test (only under medical guidance).
If you are taking thyroid hormone replacement (e.g., levothyroxine), your doctor may recommend having the blood sample collected before your daily dose for consistency.
Medical disclaimer
This article is for general information and education only. It is not medical advice, does not create a doctor–patient relationship, and is not a substitute for consultation with a qualified doctor who has assessed your individual situation. Never delay seeking medical advice because of something you have read here.
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