What it measures
- Prolactin
Why test prolactin?
Prolactin is made by the pituitary gland. It’s naturally high in pregnancy and breastfeeding, but high levels at other times can stop ovulation, cause irregular periods and reduce fertility and libido in both men and women.
Common causes of a raised result include stress, some medicines (such as certain antidepressants and anti-sickness tablets), an underactive thyroid and, less often, a small non-cancerous growth on the pituitary gland. A mildly raised result is often repeated to confirm it.
Who it’s for
- Irregular or absent periods
- Difficulty conceiving
- Milky nipple discharge when not breastfeeding
- Low libido or erectile problems in men
How to prepare
- Drink plenty of water beforehand; it makes the sample quicker and easier to take.
- You don’t need to fast.
- Try to be relaxed and rested: stress, intense exercise and nipple stimulation in the hours before can raise prolactin.
- Stop biotin (vitamin B7) supplements 48 hours before, as biotin can affect hormone and thyroid results.
Prolactin Blood Test: your questions
Can stress raise prolactin?
Yes. Physical and emotional stress, including anxiety about the blood test itself, can raise prolactin slightly. A raised result is often rechecked.
Information on this page is general and doesn’t replace advice from your GP, midwife or consultant. If you feel unwell or are worried about symptoms, contact your GP, call NHS 111 or, in an emergency, 999.