Finding the right tests…
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Finding the right tests…
Hormonal
Prolactin comes from your pituitary gland, and outside of pregnancy and breastfeeding its level should stay low, since its main job is preparing breast tissue for milk production. Your doctor orders this test when periods turn irregular or stop, when a man or woman is being investigated for infertility, or when a man has low sex drive or erectile dysfunction without an obvious cause. Because prolactin rises with stress and recent breast stimulation, the sample is usually timed for three to four hours after you wake up. A level that's high for no clear reason is often followed by an MRI of the pituitary gland, since a small, usually benign tumour called a prolactinoma is the most common cause.
This test reports the amount of prolactin in your blood, in nanograms per millilitre. Because prolactin rises with stress, sleep, and recent breast stimulation, your doctor usually asks for the sample to be drawn three to four hours after you wake up, once these short-term spikes have settled. Reference ranges differ sharply by sex and pregnancy status — pregnant women run far higher than non-pregnant women or men — so your result is read against the range that matches your situation. A single blood draw from a vein in your arm is all that's needed.
Prolactin comes from the pituitary gland, and outside of pregnancy and breastfeeding its level is normally low, since its main job is preparing breast tissue for milk production. In pregnancy, prolactin rises steadily and stays high through breastfeeding, which is expected rather than a sign of a problem.
Outside pregnancy, your doctor may check prolactin when periods have become irregular or stopped, when you or your partner are being investigated for infertility, or when a man has low sex drive, erectile dysfunction, or breast enlargement without an obvious cause. High prolactin can interfere with the hormones that drive ovulation and testosterone production, which is why it shows up in fertility workups even though it isn't itself a reproductive hormone.
The most common cause of a high prolactin level, once pregnancy is excluded, is a prolactinoma — a small, usually benign tumour of the pituitary gland. Thyroid disease, kidney disease, and several common medicines, including some antidepressants and anti-nausea drugs, can also raise it. If your level is high without an obvious explanation, your doctor will likely order an MRI of the pituitary gland and may refer you to an endocrinologist.
For men, a normal level is generally below 20 ng/mL, and for non-pregnant women, below 25 ng/mL, based on MedlinePlus reference values. In pregnancy, levels can normally run as high as 500 ng/mL. Ranges vary by lab, so check the figures printed on your own report.
Prolactin rises with stress, sleep, and recent breast stimulation, so testing three to four hours after waking helps avoid a falsely high result from these short-term spikes.
Once pregnancy is ruled out, the most common cause is a prolactinoma, a usually benign pituitary tumour, though thyroid disease, kidney disease, and certain medicines can also raise it. Your doctor will look at your full picture before deciding what's causing it.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
Yes. Some antidepressants, anti-nausea medicines, and antipsychotics are known to raise prolactin, so tell your doctor about everything you're taking before the test.
No. While a prolactinoma is the most common cause of a persistently high level, thyroid problems, kidney disease, pregnancy, and some medicines can raise prolactin without any tumour being present.
Your doctor will typically check your thyroid function and medication list first, and if there's no clear explanation, may order an MRI of the pituitary gland and refer you to an endocrinologist.