The thyroid-stimulating hormone (TSH) blood test is used to determine if your thyroid is overactive (hyperthyroidism) or underactive (hypothyroidism). It measures TSH levels, which regulate the production of T3 and T4—hormones that control metabolism. Usually paired with additional thyroid tests, this screening aids in diagnosing thyroid disorders and monitoring overall thyroid function.

Purpose of TSH Blood Test

• Assess how hypo- or hyperthyroidism treatments are working
• Identify thyroid disorders when related symptoms appear
• Examine thyroid function

How to Prepare for Your TSH Blood Test

• Drink a lot of water in the 24 hours leading up to your test to enable easier blood withdrawal.
• Wear loose-fitting clothing that provides convenient access to both hands and arms.
• If you take anticoagulants, it’s best to delay your dose until after the test. If that’s not possible, take it beforehand only if necessary.
• Let your provider know if you are afraid of needles—they’ll ensure you’re relaxed and make the process as smooth and quick as possible.