Prolactin Test: Why It Is Done and What Your Result Means

If your gynaecologist has asked for a prolactin test, it is usually because of one of three things: periods that have become irregular or stopped, milky discharge from the nipples when you are not breastfeeding, or difficulty conceiving. Prolactin is one of the most commonly ordered hormone tests in fertility workups in Pakistan, and also one of the most commonly misread, because the level moves with stress, sleep and even the blood draw itself. Here is what it does, how to test it properly, and what the numbers mean.

What prolactin does

Prolactin is a hormone made by the pituitary gland, a pea-sized gland at the base of the brain. Its main job is milk production after childbirth. High prolactin also tells the body to pause fertility, which is why exclusively breastfeeding mothers often do not ovulate. That same switch is the problem when prolactin is high in a woman who is not nursing: it can quietly suppress ovulation, and with it, periods and the chance of conceiving.

Why your doctor ordered it

The classic reasons are missed or irregular periods (see our guide to reasons periods go missing), milky nipple discharge outside breastfeeding (called galactorrhea), trouble conceiving, low libido, and sometimes persistent headaches or vision changes, which can point to a growth on the pituitary. Prolactin is usually tested alongside thyroid hormones, because an underactive thyroid can raise prolactin as a side effect; our thyroid guide explains that overlap.

How to take the test properly

Prolactin rises with sleep, stress, exercise, meals and breast stimulation, so a carelessly taken sample produces false alarms. The good-practice routine: test in the morning two to three hours after waking, sit calmly for 15 to 20 minutes before the draw, avoid heavy exercise that morning, and avoid any breast examination or stimulation the day before. The test needs no fasting at most labs. Expect to pay roughly Rs 1,000 to 2,500 at major private laboratories in Pakistan, with results the same or next day.

Normal ranges

For non-pregnant women, most labs consider roughly 2 to 25 ng/mL normal; your own lab''s reference range on the report is the one that counts. Levels are naturally much higher in pregnancy and while breastfeeding, so a "high" result in either situation is expected, not a problem. Mildly raised results (say 26 to 40 ng/mL) are very often stress or timing artefacts, and the correct next step is usually a properly prepared repeat test before any treatment.

What a genuinely high result means

Once a raised level is confirmed, common causes include hypothyroidism, several everyday medicines (some antidepressants, anti-nausea drugs and blood-pressure tablets), chest-wall irritation, and a prolactinoma, which is a small benign growth on the pituitary that overproduces the hormone. Prolactinomas sound frightening and are usually the opposite: the large majority are tiny, benign and shrink well with tablets. Very high levels (above 100 ng/mL or so) make a prolactinoma more likely and usually lead to an MRI of the pituitary.

Treatment and fertility

Treatment targets the cause. If the thyroid is the problem, treating it normalises prolactin. If a medicine is responsible, the prescribing doctor can often switch it. Prolactinomas respond very well to tablets (cabergoline or bromocriptine), which lower prolactin and shrink the growth in most women. The payoff is real: once prolactin normalises, ovulation and periods typically return within months, and many women conceive naturally afterwards. If that is your goal, our trying-to-conceive guide covers the rest of the picture, and the free Fertile Days Finder helps you spot your fertile days once cycles restart.

A note for breastfeeding mothers

High prolactin while nursing is not a disease; it is the system working. If your concern is the opposite problem, milk supply that feels too low, see our guide on increasing breast milk supply.

This article is for education and does not replace medical advice. Reviewed for accuracy by our medical review board.