Fertility & hormones
Prolactin blood test
A prolactin blood test measures a hormone made by the pituitary gland, best known for stimulating breast milk production. Outside pregnancy and breastfeeding, a high prolactin can disturb periods, fertility and libido, so it's often checked when investigating irregular cycles, unexplained infertility or hormone symptoms.
- What it measures
- Prolactin, a pituitary hormone
- Sample
- Venous blood sample
- Fasting
- Not required (best rested, not straight after exercise)
- Also known as
- PRL
- Included in 57 Health tests
- 7 panels, from £60
Prolactin reference range
Guide only| Category | Guide range |
|---|---|
| Women (non-pregnant) | < ~500 mIU/L |
| Men | < ~325 mIU/L |
Ranges are assay-dependent and higher in pregnancy and breastfeeding. Prolactin rises with stress, exercise, a recent breast examination and some medicines, so a mildly raised result is often rechecked on a calm, rested sample. A markedly high level can indicate a pituitary tumour (prolactinoma).
These are general UK adult guide ranges from public health sources, shown for orientation only. Reference ranges vary by laboratory, assay, age and sex, so your result is always interpreted against the range quoted by the analysing laboratory on your report.
What does a high prolactin level mean?
A high prolactin (hyperprolactinaemia) can stop or disrupt periods, reduce fertility and lower libido, and sometimes cause milk-like breast discharge.
Common causes include stress and some medicines; a markedly high level can indicate a benign pituitary tumour (prolactinoma). Because everyday factors raise it, a mildly high result is usually repeated on a rested sample before further assessment.
What does a low prolactin level mean?
A low prolactin is usually not clinically important on its own.
It occasionally features in broader pituitary underactivity, which would show up across several pituitary hormones rather than prolactin alone.
When to consider a prolactin test
- Irregular, infrequent or absent periods
- Difficulty conceiving
- Reduced libido or erectile difficulties
- Milk-like breast discharge (galactorrhoea)
- Investigating a possible pituitary problem
Frequently asked questions
This page is general information about a blood marker and is not medical advice or a diagnosis. A prolactin test screens and gives context; results are interpreted by a clinician alongside your symptoms, history and other markers. Always follow the guidance on your own report.