What is prolactin?
Prolactin comes from the pituitary, the gland beneath your brain that also releases LH and FSH. Its best-known task is milk production after childbirth: during pregnancy it climbs, and as long as a baby feeds it stays high. At the same time it puts the cycle on hold, and that is not a side effect but the intention: a high prolactin suppresses the release of LH and FSH, so that the ovaries rest for as long as there is breastfeeding. That brake is also the reason prolactin is measured outside breastfeeding. A prolactin that sits too high without pregnancy or breastfeeding does the same: in women the cycle becomes irregular or stays away, sometimes with milk secretion, in men LH and testosterone fall, with less desire and sometimes breast tissue as the result. Prolactin is therefore one of the first values looked at with a missing cycle, an unexplained low testosterone or little desire. Your report shows prolactin in mIU/L, at some labs written as mE/l or, a thousand times smaller, in U/l; it is the same quantity. The range sits slightly higher in women than in men, because oestrogen drives production, and it falls in women after the menopause. Normal is 86 to 278 mIU/L in men and 105 to 496 mIU/L in women up to 50 years, where the labs overlap.
Why is prolactin relevant?
Prolactin is a hormone that moves within the day itself. It rises during sleep and is still high in the first hours after waking, it rises with stress, pain, exertion and sex, with a meal, and even with the draw itself. A slightly raised value is therefore usually a moment and not a level, and is first repeated at rest: in the morning, a few hours after getting up, rested, and not after exercise or sex. If it stays raised, there are three usual explanations. The first is medicines: anti-nausea drugs such as metoclopramide and domperidone, many antipsychotics and some antidepressants block dopamine, the brake on prolactin, and lift it sharply. The second is an underactive thyroid, because the hormone that drives the thyroid also drives prolactin; TSH shows it. The third is a prolactinoma, a benign nodule in the pituitary that makes prolactin. That sounds more serious than it is: it is the most common pituitary tumour, almost always benign, and usually treatable with tablets that shrink the prolactin and the nodule together. There is a fourth, harmless explanation: macroprolactin, a large form of the hormone that counts in the measurement but does nothing. It can be tested for, and with a raised prolactin without complaints that is the first question. Lifestyle is not a big lever for prolactin, apart from two things: sleep and stress. Anyone who structurally sleeps too little or lives under lasting stress measures higher values, and that carries through into the cycle and desire. Beyond that, prolactin is above all a value to measure well and read well.
Prolactin reference ranges
What counts beside the number:
- How the measurement went: time, sleep, stress, exertion, sex and a meal beforehand
- The unit on your report: mIU/L, mE/l or U/l are the same quantity, written a thousand times apart
- Medicines that block dopamine, the most common persistent and reversible cause
- TSH, because an underactive thyroid raises prolactin
- LH, FSH and oestradiol or testosterone, the hormones a high prolactin suppresses
- Symptoms: a missing cycle, milk secretion, little desire, headache or a blurred side field of vision
The bands above are where the labs overlap; the range on your own report may be wider, and there is no national normal value. Mind the unit: mIU/L, mE/l and U/l are the same quantity, and U/l is written a thousand times smaller. All bands apply to a measurement at rest, in the morning a few hours after getting up; a slightly raised value is first repeated that way.
What Dutch labs actually use
The four labs measure prolactin in the same quantity and write it down differently. Unilabs reports in U/l, Star-shl in mE/l, Certe and Clinical Diagnostics in mIU/L, and those three notations mean the same thing: 0.410 U/l is 410 mIU/L. A factor of a thousand in the notation, not in your blood. The second difference is age. Star-shl and Clinical Diagnostics split women at the fiftieth year, Unilabs and Certe do not: Star-shl holds a woman from 19 through 50 yrs under 860 mIU/L and above that under 590 mIU/L, Clinical Diagnostics holds her under fifty at 71 to 566 mIU/L and after that at 58 to 416 mIU/L. Where all four overlap, a man is left with 86 to 278 mIU/L, a woman up to age 50 with 105 to 496 mIU/L and from age 50 with 105 to 416 mIU/L. For women the floor comes in both cases from Unilabs, converted 105 mIU/L.
105 – 496mIU/L
Between 0 and 105 and between 496 and 860 it depends on the lab, because each sets its limits on its own method and population. Above 860 every lab calls it abnormal.
every lab calls 105 – 496 mIU/L normal. Between 0 and 105 and between 496 and 860 it depends on the lab.
Every age, per lab
| Laboratory | Group | Reference range |
|---|---|---|
| Unilabs(Saltro, Medlon, SHO, Atalmedial)2026 | Men | 0.070–0.410 U/l |
| Women | 0.105–0.560 U/l | |
| Star-shl2026 | 1 to 19 yrs | 64–532 mIU/L |
| Men from 19 yrs | < 550 mIU/L | |
| Women 19 through 50 yrs | < 860 mIU/L | |
| Women above 50 yrs | < 590 mIU/L | |
| Certe2026 | Women from 18 yrs | 102–496 mIU/L |
| Men from 18 yrs | 86–324 mIU/L | |
| Clinical Diagnostics2026 | Men | 56–278 mIU/L |
| Women up to 50 yrs | 71–566 mIU/L | |
| Women from 50 yrs | 58–416 mIU/L |
Each band as the lab publishes it, retrieved in 2026, unless marked otherwise.
Prolactin high or low: what it means
A raised prolactin starts with the question of how the measurement went: shortly after waking, after exertion, sex, a meal or a stressful draw, then a repeat at rest is the first step. If it stays slightly to moderately raised, medicines that block dopamine, an underactive thyroid, pregnancy and macroprolactin are the usual explanations, in that order. A strongly raised value, a multiple of the range, fits a prolactinoma, and then an MRI of the pituitary belongs to it. In women a missing cycle or milk secretion comes with it, in men a low testosterone. A low prolactin almost never means anything. It occurs with medicines that mimic dopamine, such as drugs for Parkinson's disease and the tablets for a prolactinoma, and very rarely with a pituitary that makes too little as a whole; then other pituitary hormones are abnormal too. What you can do yourself is make the measurement clean and know the levers there are: enough sleep, less lasting stress, and with a raised value checking which medicines you take, because that is where the most common reversible cause sits. A prolactinoma or an underactive thyroid are very treatable, and the cycle and testosterone then return. Read prolactin beside LH and FSH, the hormones it suppresses, beside oestradiol or testosterone, the consequence of that, and beside TSH, because an underactive thyroid raises it. Compare over time in the same unit and at the same lab.
What lowers it
Rarely of any significance.
| Cause | How often |
|---|---|
| Medicines that mimic dopamineDrugs for Parkinson's disease and the tablets for a prolactinoma suppress prolactin; a low value is then the intention | Rare |
What raises it
Usually the moment of the measurement; persistently, usually medicines, the thyroid or a benign nodule.
| Cause | How often |
|---|---|
| The draw itselfThe needle and the tension around it lift prolactin temporarily; a slightly raised value is therefore first repeated at rest | Often |
| Stress or too little sleepProlactin rises during sleep and with stress, pain, exertion and sex; shortly after waking it is still high | Often |
| Pregnancy and breastfeedingThe ordinary reason for a high prolactin: it climbs in pregnancy and stays high as long as a baby feeds | Often |
| Medicines that block dopamineMetoclopramide and domperidone for nausea, most antipsychotics and some antidepressants block the brake on prolactin and lift it sharply | Sometimes |
| Underactive thyroidThe hormone that drives the thyroid also drives prolactin; TSH shows it and treating the thyroid normalises it | Sometimes |
| MacroprolactinA large, inactive form of the hormone that counts in the measurement; the lab can test for it, and then the rise is harmless | Sometimes |
| ProlactinomaA benign nodule in the pituitary that makes prolactin; the value then usually sits a multiple above the range, and tablets shrink the nodule and the value | Rare |
How does a prolactin blood test work?
- Referral
- Not needed. You can have prolactin measured without going through your GP.
- When to draw
- In the morning, two to three hours after getting up, rested and relaxed. Not after exercise, sex or a heavy meal, and not as the first draw after a rushed morning.
- Fasting
- Not strictly needed, but a meal lifts prolactin temporarily; a light breakfast is no problem.
- The draw
- One tube of blood from a vein in your arm. With a tense draw the lab does better to take the tube a few minutes later, after sitting quietly for a moment.
- The result
- A single number in mIU/L, mE/l or U/l; the same quantity in three notations. With a raised value some labs test for macroprolactin.
- Repeating
- A slightly raised value always first repeated at rest. If it stays raised, TSH and a medication list belong to it, and with a strongly raised value an MRI of the pituitary.
- Where to draw
- You can draw at 250+ locations near you, no referral needed. See the locations
Frequently asked questions
What is prolactin?
A hormone from the pituitary, the gland beneath your brain, that starts milk production after childbirth and at the same time puts the cycle on hold for as long as there is breastfeeding. Outside that time it acts as a brake on your sex hormones: a raised prolactin suppresses LH and FSH, and with them the cycle, desire and testosterone. That is why it is measured with a missing cycle or a low testosterone.
What is a normal prolactin level?
In men 86 to 278 mIU/L, in women up to 50 years 105 to 496 mIU/L and after that 105 to 416 mIU/L, measured at rest. The range on your own report may be wider, and mind the unit: some labs write mE/l, and one lab U/l, which looks a thousand times smaller but is the same.
What does a raised prolactin mean?
Usually first: how did the measurement go? Shortly after waking, after exercise, sex, a meal or a tense draw prolactin sits temporarily higher, and then a repeat at rest is the first step. If it stays raised, medicines that block dopamine, an underactive thyroid, pregnancy and macroprolactin are the usual explanations. A value a multiple above the range fits a prolactinoma, a benign nodule in the pituitary that can be treated with tablets.
What does a low prolactin mean?
Almost never anything. It occurs with medicines that mimic dopamine, such as drugs for Parkinson's disease and the tablets for a prolactinoma, and very rarely with a pituitary that makes too little as a whole; then other pituitary hormones are abnormal too.
Which medicines raise prolactin?
Above all drugs that block dopamine, because dopamine is the brake on prolactin: metoclopramide and domperidone for nausea, most antipsychotics and some antidepressants. The pill and hormone therapy lift it a little too. With a raised value the medication list is therefore the first place to look, and after stopping or switching the value falls again.
What is a prolactinoma, and is it serious?
A benign nodule in the pituitary that makes prolactin. It is the most common pituitary tumour and almost always benign; it gives a strongly raised prolactin, in women a missing cycle and sometimes milk secretion, in men a low testosterone, and with a larger nodule headache or a blurred side field of vision. Treatment usually consists of tablets that shrink the prolactin and the nodule together.
Can a prolactin level be temporarily higher?
Yes, easily. Prolactin rises during sleep and is still high in the first hours after waking; stress, pain, exertion, sex, a meal and the draw itself lift it too. One slightly raised value is therefore usually a moment and not a level, and is repeated at rest before anything is drawn from it.
How do I prepare for a prolactin test?
Have blood drawn in the morning, two to three hours after getting up, rested and relaxed. No exercise, sex or heavy meal beforehand; a light breakfast is no problem. Have LH, FSH and TSH taken in the same draw, and compare over time in the same unit at the same lab.
Which tests include prolactin?
Prolactin is in the Hormones men test (€129, also as an add-on for €109).
Related biomarkers
Read on
Sources
- 1.Unilabs, test catalogue (Dutch): prolactin. 2026. bepalingenklapper.nl
- 2.Star-shl, test catalogue (Dutch): prolactin. 2026. star-shl.nl
- 3.Certe, test catalogue (Dutch): prolactin. 2026. bepalingenwijzer.certe.nl
- 4.Clinical Diagnostics, lab guide (Dutch): prolactin. 2026. clinicaldiagnostics.nl
Educational information only, not medical advice. Consult a healthcare professional for clinical decisions.
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