Prolactin
What it measures, and what changes the number.
Prolactin is a hormone made by the pituitary gland at the base of the brain. It is best known for its role in milk production, but it is present in everyone and is also linked to reproductive hormone signaling. The test measures its level in blood.
It is commonly ordered with LH, FSH, estradiol or testosterone when reproductive hormones are being looked at, and with TSH because thyroid function can influence prolactin.
Prolactin rises with stress, including the stress of the needle, with sleep, exercise and breast stimulation, so labs often prefer a relaxed draw some time after waking, and a repeat may be requested. Some people have large prolactin complexes called macroprolactin that react in immunoassays; labs can test for this separately. It may be reported as Prolactina or PRL.
Reference ranges labs publish
Each lab states an interval for its own method and the population it measured. They differ, they are not interchangeable, and none of them is a verdict on a single result.
- Men, 18 years and over: 4 to 15.2 ng/mL · ECLIA (immunoassay) · Source: Mayo Clinic Laboratories, PRL (Prolactin, Serum) (read 2026-09-24)
- Men, 13 to 30 years: 3.6 to 31.5 ng/mL · ECLIA (immunoassay) · Source: Labcorp, 004465 (Prolactin) (read 2026-09-24)
- Men, 31 to 50 years: 3.9 to 22.7 ng/mL · ECLIA (immunoassay) · Source: Labcorp, 004465 (Prolactin) (read 2026-09-24)
- Men, 51 to 80 years: 3.6 to 25.2 ng/mL · ECLIA (immunoassay) · Source: Labcorp, 004465 (Prolactin) (read 2026-09-24)
- Men, 81 years and over: 3.6 to 32 ng/mL · ECLIA (immunoassay) · Source: Labcorp, 004465 (Prolactin) (read 2026-09-24)
- Women, 18 years and over: 4.8 to 23.3 ng/mL · ECLIA (immunoassay) · Source: Mayo Clinic Laboratories, PRL (Prolactin, Serum) (read 2026-09-24)
- Women, 13 to 50 years: 4.8 to 33.4 ng/mL · ECLIA (immunoassay) · Source: Labcorp, 004465 (Prolactin) (read 2026-09-24)
- Women, 51 to 80 years: 3.6 to 25.2 ng/mL · ECLIA (immunoassay) · Source: Labcorp, 004465 (Prolactin) (read 2026-09-24)
- Women, 81 years and over: 3.6 to 32 ng/mL · ECLIA (immunoassay) · Source: Labcorp, 004465 (Prolactin) (read 2026-09-24)
Often read alongside: TSH, LH, FSH, Estradiol (E2), Total testosterone