Prolactin

The normal reference range for Prolactin is Roughly under 500 mIU/L in non-pregnant women and under 400 mIU/L in men, though ranges vary by lab. Levels are naturally high in pregnancy and breastfeeding. Mildly raised results are common and often due to stress or the blood draw itself, so they are usually rechecked before being acted on.. Reference ranges may vary between laboratories, so always consult your healthcare provider for interpretation.

Helps diagnose causes of irregular menstruation, fertility issues, and certain pituitary disorders.

Prolactin rises with pregnancy, breastfeeding, nipple stimulation, stress and even the stress of the needle. Persistently high levels (hyperprolactinaemia) are most often caused by a benign pituitary tumour (prolactinoma), an underactive thyroid, or medications — particularly antipsychotics, some antidepressants, anti-nausea drugs (metoclopramide) and opioids. A high reading can be a lab artefact called macroprolactin, which should be excluded. Excess prolactin suppresses sex hormones, causing irregular or absent periods, low libido, erectile dysfunction and sometimes milk discharge.

Low prolactin is rarely clinically significant. It can occur with pituitary failure (hypopituitarism) or with dopamine-agonist medication (such as cabergoline or bromocriptine, which are used to treat high prolactin). On its own, a low level usually needs no action.

Prolactin is best drawn in the morning, ideally after resting quietly for 15-30 minutes, avoiding nipple stimulation and strenuous exercise beforehand. A mildly elevated result is typically repeated under relaxed conditions, with macroprolactin testing if it remains high. Once a cause (such as a prolactinoma) is being treated, it is monitored periodically.