Check your thyroid hormone at home.

It tells you whether your thyroid-stimulating hormone (TSH) is above 5 µIU/mL. TSH is the signal your pituitary gland sends to tell your thyroid to get to work. When the thyroid is underactive, TSH usually climbs — which is why doctors use it as the first check for an underactive thyroid (hypothyroidism). This test gives you a clear above-or-below answer at that threshold, not an exact number.

Feeling tired, low or cold a lot of the time. Weight gain, dry skin, brittle hair, ongoing constipation, or changes to your menstrual cycle. These are easy to put down to a busy life, and they overlap with plenty of other things. A TSH check is a simple way to see whether your thyroid is part of the picture.

No. A full panel usually also measures the thyroid hormones T4 and T3, and sometimes thyroid antibodies. This test checks TSH only — the marker most often used as a first step. If your result is positive, your doctor can order the fuller picture.

No. This test isn't designed for people on thyroid hormone treatment. If you're already being treated, your levels should be monitored with the lab tests your doctor orders.

Adults who want to screen for an underactive thyroid. It isn't for newborns or children. If you're pregnant or have a known thyroid condition, talk to your doctor about which test is right for you.

Two lines — Control (C) and Test (T) — mean your TSH is higher than 5 µIU/mL, which is above the normal range. Show the result to your doctor. They'll usually confirm it with a lab test that measures your exact level and decide whether anything else is needed. A faint T line still counts as positive.

Only the Control (C) line means your TSH is below 5 µIU/mL, within the normal range. It doesn't rule out an overactive thyroid (hyperthyroidism), which this test isn't designed to pick up, or rarer conditions where the problem starts in the pituitary gland. If you still have symptoms, talk to your doctor.

In a clinical evaluation of 220 blood samples compared with a laboratory method (ELISA), this test agreed 98.2% of the time. Like any screening test it can occasionally be wrong, which is why a positive result should always be confirmed with a lab TSH test.

Any time of day.

Read your result 10 minutes after you add the buffer drops. Don't read it after 20 minutes — it's no longer reliable. A timer isn't included, so have your phone ready.

Most people feel a quick pinch. The lancet is single-use and its tip retracts on its own. Washing your hands in warm water first helps blood flow, and the side of your ring finger is usually the most comfortable spot.

No. What matters is whether a line is there, not how dark it is. Any visible T line alongside the C line is a positive result.

The test didn't run correctly, so there's no result to read. It usually means there wasn't quite enough blood or a step was missed. Use a new test, and contact us if it happens again.