What this test measures
Prolactin (PRL) is a pituitary hormone secreted by lactotroph cells. It is the main hormone of lactation but also has roles in immune regulation, fluid balance and behaviour. Prolactin is normally suppressed by dopamine from the hypothalamus; anything that lowers dopamine (or blocks its receptor) raises prolactin.
Levels rise transiently with sleep, exercise, stress, breast stimulation and meals, so a true baseline should be drawn in the late morning, well-rested, without prior nipple stimulation. Macroprolactin — a biologically inactive antibody-prolactin complex — can cause falsely raised results and should be excluded with a PEG-precipitation test if a high prolactin is otherwise unexplained.
Why it matters
Hyperprolactinaemia is the commonest pituitary hormone abnormality seen in Indian clinics and is one of the most reversible causes of female amenorrhoea, subfertility and galactorrhoea, and of male hypogonadism and erectile dysfunction. Drug-induced hyperprolactinaemia is far commoner than tumours — antipsychotics (risperidone, haloperidol, paliperidone), antidepressants, domperidone, ranitidine and methyldopa all raise prolactin substantially.
If drug effect and hypothyroidism (which also raises prolactin) are excluded, persistently raised prolactin above 100–200 ng/mL warrants a pituitary MRI. Microprolactinomas are usually treated medically with dopamine agonists (cabergoline, bromocriptine) — surgery is reserved for the few cases that do not respond.
How to prepare
Sample is best drawn in the late morning (10 am – noon), at least 1 hour after waking and at least 2 hours after a meal. Avoid significant breast or nipple stimulation in the hour before. Stop biotin for 48–72 hours. Tell your doctor about all medications — many over-the-counter and prescription drugs raise prolactin.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Prolactin (ng/mL)[1][2] | Adult female (non-pregnant): 4.8 – 23.3 · Adult male: 4.0 – 15.2 · Pregnancy: 10 – 290 (rising through trimesters) | Low prolactin rarely matters in isolation. Suggests panhypopituitarism if other pituitary hormones (TSH, LH, FSH, cortisol) are also low. Bromocriptine and cabergoline lower prolactin (expected drug effect). | 25–100 ng/mL — drug effect, hypothyroidism, stress, recent breast stimulation, pregnancy. 100–200 — micro-prolactinoma likely. > 200 — macro-prolactinoma likely; arrange pituitary MRI. Mildly raised prolactin in a normal-feeling person may be macroprolactin (biologically inactive) — exclude with a PEG-precipitation test. |
Prolactin levels and likely causes
| Prolactin (ng/mL) | Likely cause | Action |
|---|---|---|
| < 25 | Normal | No action |
| 25 – 100 | Drug effect, stress, hypothyroidism, macroprolactin | Review meds, check TSH, PEG test |
| 100 – 200 | Microprolactinoma likely | Pituitary MRI, consider cabergoline |
| > 200 | Macroprolactinoma likely | Pituitary MRI, cabergoline; visual field testing |
| Pregnancy | Up to 290 | Physiological |
Frequently asked questions
Why is the blood draw timing important for prolactin?
Prolactin rises during sleep and after meals or breast stimulation. A late-morning sample, well after waking and at least 2 hours after eating, gives the most reliable baseline.
My prolactin is high — does that mean I have a tumour?
Not necessarily. Drug effect (antipsychotics, domperidone, anti-emetics) is the commonest cause, followed by hypothyroidism. If those are excluded and prolactin remains > 100 ng/mL on repeat testing, a pituitary MRI is indicated.
What is macroprolactin?
A large, biologically inactive form of prolactin (an antibody-prolactin complex) that can falsely raise the prolactin reading. If a raised prolactin is asymptomatic, ask your lab to perform a polyethylene glycol (PEG) precipitation to check for macroprolactin.
I am a man with low libido and erectile dysfunction — should I check prolactin?
Yes. Hyperprolactinaemia suppresses GnRH, lowering LH and testosterone and causing exactly these symptoms. It is one of the treatable causes of male hypogonadism and is part of the standard workup along with testosterone, LH and FSH.
What treatment is used for prolactinoma?
Dopamine agonists — usually cabergoline (preferred for tolerability and efficacy) or bromocriptine. Most micro- and macro-prolactinomas shrink and prolactin normalises on medication. Surgery is reserved for non-responders and patients intolerant of medication.
Can stress on the day of the test raise prolactin?
Acute stress (anxiety, exercise, a difficult blood draw) can mildly raise prolactin. Mention this if the result is borderline; a repeat sample under relaxed conditions is reasonable.
Will pregnancy affect prolactin?
Yes — prolactin rises 10–20 fold through pregnancy and stays high during breastfeeding. Pregnancy-specific reference ranges apply.
Related Hormones / Endocrine tests
Tests commonly ordered alongside PROLACTIN (PRL), or that help interpret an unexpected result.
Sources & references
- Endocrine Society — Hyperprolactinemia Guideline · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — Prolactin Test · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Prolactin · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Laboratories — Prolactin · accessed 2026-05-30T00:00:00.000Z
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