What TSH measures
TSH is made by the pituitary gland and tells the thyroid how much hormone to produce. When thyroid hormone levels drop, TSH rises to push the thyroid harder; when they're high, TSH falls.
Because it responds so sensitively, TSH is usually the first thyroid marker measured. Many panels add free T4 (FT4) and free T3 (FT3), and some include thyroid antibodies.
Why it matters for longevity
Thyroid hormones set the pace of metabolism and affect energy, weight, heart rate, body temperature and mood.
Thyroid function also influences other results – for example, cholesterol and ApoB can be higher when the thyroid is underactive. Tracking TSH gives you a baseline to compare against if anything changes.
How it's tested
- Sample
- Finger-prick or venous
- Fasting
- Not needed
- Units
- mIU/L
Before you test
- Biotin (vitamin B7) can interfere with some lab methods – providers often ask you to stop it for a few days before testing.
- TSH is a little higher in the early morning, so test at a similar time each time.
What can affect your result
- Biotin supplements
- Recent illness and recovery
- Pregnancy
- Thyroid medicines and some other medicines
Talking to your doctor about your result
Your report will show your result next to the lab's reference range. Ranges differ between labs and units, and a result inside or outside the range isn't a diagnosis on its own. Share the full report with your doctor – especially if a result is flagged, you have symptoms, or there's a family history that concerns you. Don't start, stop or change any medicine or supplement based on a home test without medical advice.
What a TSH test costs
In our European price check (12 October 2026), the cheapest Thyroid test or small panel we found was €17 (Labor Dr. Heidrich (Hamburg), Germany); the cheapest option in the most expensive country was €53 (United Kingdom). Lab prices often exclude a small blood-draw or visit fee. It can be better value as part of a panel if you want several of the core markers. See every price by country in our European blood test price guide.
TSH: common questions
Is TSH enough on its own?
TSH is a good first check, but many providers add free T4 because the two together give a clearer picture. Your doctor may ask for more tests depending on the result.
Do I need to stop supplements before a thyroid test?
Biotin, found in many hair, skin and nail supplements, can affect some thyroid assays. Providers often ask you to stop it a few days before testing – check their instructions, and don't stop prescribed medicines without asking your doctor.
Why test thyroid function if I'm interested in longevity?
Thyroid function affects energy, weight and cholesterol, so it helps explain changes in your other markers. A baseline result is useful to compare against later.
Related markers
Sources
[PLACEHOLDER: 2–4 primary references (guidelines, consensus statements) confirmed by the medical reviewer]