Good to knowOne result rarely tells the whole story. Your provider looks at your results together with your symptoms, exam, and other tests.
What the test is
Stress, nipple stimulation, and some medicines can raise it.
Why it's done
- Missed periods or infertility
- Milky nipple discharge when not breastfeeding
- Low sex drive or erection problems
- Headaches or vision changes (possible pituitary tumor)
Getting ready and what happens
- Test in the morning, a few hours after waking, and avoid nipple stimulation beforehand.
How the test is done
- A health worker cleans the skin, puts a band around your arm, and draws blood from a vein with a small needle. It takes a few minutes.
What the results mean
High
Causes include pregnancy, some antipsychotics and other medicines, an underactive thyroid, and benign pituitary tumors (prolactinomas).
Questions to ask your provider
- What do my results mean for me?
- Do I need to repeat this test or have other tests?
Risks
A blood draw is very safe. You may have slight pain or a small bruise where the needle went in.
Related conditions
Related medicines
Related tests
Sources
Last updated 2026-11-13.