Fertility Library · 2026-10-13
High Prolactin on a Fertility Blood Test: Should You Repeat It?
Short answer: a mildly raised prolactin result may need confirming before anyone treats it as a persistent condition. A flagged result alone cannot diagnose a fertility problem.
Why is prolactin checked?
Prolactin is a hormone made by the pituitary gland. Persistently high levels can sometimes disrupt reproductive hormone signalling and ovulation, particularly when periods are infrequent or absent. A result must be read alongside symptoms, medicines, the laboratory range and the reason for testing.
Why can one result be high?
Sleep, exercise, nipple stimulation, stress around blood sampling, pregnancy, breastfeeding and certain medicines can raise prolactin. Thyroid disease and some pituitary conditions are other possible causes. Do not stop prescribed medication on your own.
When should it be repeated?
ASRM's 2024 amenorrhoea guidance advises confirming mild elevations before diagnosing hyperprolactinaemia. Ask whether a repeat sample is useful, whether the laboratory has special collection instructions and what would change the next step. Some laboratories recommend rest before collection.
What is macroprolactin?
Some tests detect a larger form of prolactin called macroprolactin, often with less biological activity. If the result remains mildly elevated but symptoms do not fit, a clinician may request macroprolactin assessment rather than assuming the total value explains fertility concerns.
Does a high result mean a tumour?
No. A prolactinoma is only one potential explanation. Scans are not automatically needed after one mildly elevated blood result. Sudden severe headache or new visual changes require urgent assessment.
Questions to ask
- How high is my result relative to this laboratory's reference range?
- Should we repeat it, and how should I prepare?
- Could medicines, thyroid function or macroprolactin affect interpretation?
- What other fertility investigations are relevant?
See our fertility hormone testing guide and irregular periods guide.
Evidence
ASRM: Current evaluation of amenorrhea (2024); NICE fertility assessment guidance (2026).
Find the next questions to ask
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