A TSH blood test measures the level of thyroid-stimulating hormone in your bloodstream. TSH is produced by the pituitary gland and tells your thyroid how much hormone to make. Doctors use this test to screen for hypothyroidism, hyperthyroidism, and to monitor thyroid medication.
What Does a TSH Blood Test Measure?
TSH testing checks how well your thyroid is working. When thyroid hormone levels drop, the pituitary releases more TSH to stimulate production. When thyroid hormones are high, TSH drops. This makes TSH a sensitive early indicator of thyroid dysfunction — often changing before T3 and T4 levels do.
Why Do Doctors Order a TSH Test?
- Screening for hypothyroidism (underactive thyroid)
- Screening for hyperthyroidism (overactive thyroid)
- Checking symptoms like fatigue, weight changes, or temperature sensitivity
- Monitoring levothyroxine or other thyroid medications
- Evaluating fertility issues or irregular periods
How Is the TSH Test Done?
The test requires a simple blood draw from a vein in your arm. You typically do not need to fast for a TSH test, though some doctors may ask you to avoid biotin supplements for 48 hours beforehand. Results are usually available within 1–2 business days.
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Most adults have a TSH level between 0.4 and 4.0 mIU/L. Higher TSH usually means an underactive thyroid, while lower TSH suggests an overactive thyroid. For a detailed breakdown, see our TSH levels guide or normal TSH levels page.
Upgrade to a Full Thyroid Panel
If you want a complete picture of your thyroid health, consider a full thyroid panel which includes TSH, Free T3, Free T4, and TPO antibodies. This is especially useful if you have a family history of thyroid disease or autoimmune conditions.
Frequently Asked Questions
Do I need a doctor's order for a TSH test?
No. You can order a TSH blood test online and visit a local lab directly.
How much does a TSH test cost?
Self-pay TSH tests typically range from $35–$70 when ordered online. Full thyroid panels cost more but offer deeper insight.
Should I test TSH alone or with T3 and T4?
TSH alone is an excellent screening tool. If results are abnormal or symptoms persist, adding Free T3 and Free T4 gives a more complete picture.
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