Prolactin
A pituitary hormone best known for lactation, but clinically important in both sexes — elevation suppresses the entire reproductive axis.
High prolactin is a correctable cause of low testosterone, low libido and ED that gets missed when only testosterone is measured. In women it causes cycle irregularity and infertility.
The plan of attack
In this order. Most people start at step four, which is why they change five things at once and learn nothing.
- Confirm the number is real
Macroprolactin. A biologically inactive prolactin-antibody complex that the assay counts as prolactin. It causes a substantial minority of raised results, in people with no symptoms at all — and has led to unnecessary pituitary imaging. Ask the lab to check for macroprolactin before any scan. - Read it with its partner
Any unexplained low libido or ED despite adequate testosterone should trigger a prolactin check — it's cheap and frequently the answer. Draw it alongside: Total Testosterone, LH & FSH, TSH (Thyroid-Stimulating Hormone). - Work out which direction is yours
If it's high — Low libido, ED, infertility, galactorrhea, cycle irregularity. Markedly elevated values warrant pituitary MRI. Note prolactin rises with stress and even the venipuncture itself — repeat a mildly high value before acting.
If it's low — Rarely clinically significant. - Fix it in this order
Nutrition. No direct dietary lever. Correct hypothyroidism, which is a common secondary driver.
Lifestyle. Reduce stress, address sleep. Re-draw fasted, rested, and having avoided orgasm/nipple stimulation for 24h.
Supplements. Vitamin B6 (P5P) has modest dopaminergic prolactin-lowering effects. Zinc supports dopamine. Vitex is used in women but should be discussed with a provider.
Hormones. Dopamine agonists (cabergoline, bromocriptine) are the medical treatment — prescription only, with real side effects, and not something to self-administer. Treat underlying hypothyroidism first.
Compounds. Relevant for anyone who has used 19-nor compounds. No peptide lowers prolactin.
Work down the list, not across it. Adding a compound on top of an unfixed diet is why generic protocols fail. - Retest
Repeat any elevated value before acting; then per provider. Change one thing at a time, or the retest can't tell you which thing worked.
How to fix it
📚 Endocrine Society CPG — Diagnosis and Treatment of Hyperprolactinemia.
🩸 Test your Prolactin
Order directly through Marek Diagnostics — no doctor's visit needed, drawn at any Quest location in the US. Code CAMERON applies 10% off automatically.
Order this test — 10% off → Browse all 102 markers →What Prolactin is usually tested alongside
On its own, one marker is a data point. These panels include Prolactin plus the markers that make it interpretable — each names every test, why it is on the list, and loads the whole set into your cart in one click at 10% off.
includes this + 10 more markers · built for men — Fatigue, low libido, poor recovery, mood or body composition changes — and you're considering TRT. Read this before you start.
includes this + 10 more markers · built for men — Erectile difficulty, reduced spontaneous erections, or a libido that's dropped and hasn't come back.
includes this + 9 more markers · built for women — Planning a pregnancy, actively trying, or wanting to understand your ovarian reserve before making decisions about timing.
includes this + 9 more markers · built for women — Irregular or absent periods, acne, unwanted hair growth, scalp thinning, difficulty losing weight, or you've been told 'probably PCOS' without a workup.
What moves your Prolactin
5 compounds and 1 supplement in the Vault have a documented effect on this marker, or are a reason to have measured it first:
Browse all 237 compounds & 350 supplements →
Would you feel it? Symptoms Prolactin helps explain
People rarely search for a marker — they search for how they feel. These are the complaints where this marker is worth checking, and whether it is a first-line test or a follow-up once the obvious causes are ruled out.
Why your Prolactin might be wrong
Most abnormal results are interference, not disease. These are the things that measurably move this specific marker — check them before you change anything. Each one says whether the number is wrong and should be repeated, badly timed and should be redrawn, or real with a cause worth explaining.
All raise prolactin transiently, sometimes substantially. Even the stress of a difficult venepuncture can do it.
Morning, rested, and not after a breast exam, exercise or sex. Always repeat a borderline result before acting on it.
A biologically inactive prolactin-antibody complex that the assay counts as prolactin. It causes a substantial minority of raised results, in people with no symptoms at all — and has led to unnecessary pituitary imaging.
Ask the lab to check for macroprolactin before any scan.
At very high prolactin levels some assays paradoxically report a near-normal result.
If the clinical picture strongly suggests a prolactinoma but prolactin is only mildly raised, ask for a diluted repeat.
Dopamine-blocking drugs raise prolactin substantially and are a far more common cause than a tumour.
Review medications first.
What Prolactin means in combination
A single marker tells you a little. Combinations tell you the story — these are the named patterns this marker takes part in, and what each one points at.
Prolactin suppresses the gonadal axis and blunts libido independently of testosterone. It gets blamed on estradiol constantly, and the AI that follows makes things worse.
Repeat the draw before acting — prolactin rises with stress, sleep, food and the needle itself. Persistent elevation with headaches or vision changes needs pituitary imaging. Rule prolactin out before you touch an AI.
19-nor compounds raise prolactin, which suppresses the axis and causes sexual dysfunction that's often misattributed to estradiol.
Confirm with a repeat draw (prolactin rises with stress and the needle itself). Address with a physician — dopamine agonists are prescription medications with real side effects, not casual additions. Rule out prolactin before blaming E2 and reaching for an AI.
What to test next
Markers rarely answer alone. These are the ones that put Prolactin in context — each with its own full breakdown.
Frequently asked questions
4–15.2 ng/mL Ranges vary by laboratory and assay — always compare to the range printed on your own report.
Low-to-mid range.
Low libido, ED, infertility, galactorrhea, cycle irregularity. Markedly elevated values warrant pituitary MRI. Note prolactin rises with stress and even the venipuncture itself — repeat a mildly high value before acting.
Rarely clinically significant.
You can order Prolactin directly through Marek Diagnostics without a doctor's visit — drawn at any Quest Diagnostics location in the US. Code CAMERON applies 10% off automatically.