The short answer: FSH (follicle-stimulating hormone) and LH (luteinising hormone) are made by your pituitary gland to tell your ovaries to grow and release eggs. As your ovaries wind down, they respond less, so your brain shouts louder and FSH rises. A sustained FSH above roughly 30 mIU/mL on repeat testing, alongside no periods for a year, points to menopause and low estrogen (oestrogen). Here is the honest part most people are not told: if you are over 45, a single FSH blood test is an unreliable way to diagnose perimenopause, because levels swing wildly from day to day and month to month. NICE guidance advises diagnosing perimenopause and menopause in this age group from your symptoms, not from bloods. FSH testing genuinely helps in specific situations, which we cover below.
If your GP glanced at your results and said “your bloods are normal” while you feel like a different person, you are not imagining it and you are not alone. Thousands of women describe the same scene: night sweats, a brain like cotton wool, periods that vanish for two months then return with a vengeance, and a lab report that says everything is fine. The problem is not you. It is that a one-off hormone snapshot often cannot capture a system that is lurching, not gliding, toward the finish line. Understanding what FSH and LH actually measure makes that conversation with your clinician far more useful.
What are FSH and LH?
FSH and LH are gonadotrophins, hormones released by the pituitary gland at the base of your brain to control your ovaries. FSH prompts a batch of follicles to mature each cycle, and LH triggers ovulation, the release of an egg roughly mid-cycle. They work in a feedback loop with the hormones your ovaries make, chiefly estrogen (oestrogen) and progesterone.
In your reproductive years, when a follicle grows, it produces estrogen, which signals the pituitary to ease off on FSH. This is a thermostat: enough ovarian hormone, and the brain turns the dial down. When the ovaries respond poorly, the estrogen signal weakens, so the thermostat never gets its “stop” message and keeps pushing FSH higher.
LH behaves similarly and also climbs as the ovaries age, though FSH is the number clinicians watch most for menopause, because it rises earlier and more reliably. For a broader picture of the hormones at play, see our guide to perimenopause hormones explained.
Why does FSH rise in menopause?
FSH rises because your ovaries are running low on responsive follicles. You are born with a finite pool of eggs, and that pool shrinks across your life. By your 40s and 50s, the follicles that remain are fewer and less responsive to FSH, so the pituitary compensates by producing more of it to try to coax a response.
Think of it as a quieter room forcing someone to raise their voice. The ovaries have gone quiet; the pituitary gets louder. A high FSH, therefore, is not a sign your pituitary is broken. It is a sign your ovaries are no longer answering, which is the defining event of menopause.
Postmenopausally, with almost no follicles left to respond, FSH stays persistently high and estrogen stays low. This is why a single high FSH reading means something quite different at 58 with no periods for two years than it does at 46 with irregular cycles.
What FSH level means menopause?
A sustained FSH above roughly 30 mIU/mL, measured on more than one occasion, is the level commonly used to indicate a menopausal pattern, especially when periods have stopped for 12 months. Many postmenopausal women show FSH well above 30, often in the 40 to 100 mIU/mL range, while estradiol (the main form of estrogen before menopause) falls low.
These numbers are approximate and lab-dependent. Reference ranges differ between laboratories and between the phases of your cycle, so always read your own result against your own lab’s stated range and ideally with a clinician who knows your history. A table of typical patterns is below.
The key word is pattern. One number on one day is a data point. A repeated pattern of high FSH with low estradiol and no periods is a diagnosis. This distinction is the heart of why testing is often less helpful than it sounds for women in their mid-40s and beyond.
| Stage | FSH (mIU/mL) | LH (mIU/mL) | Estradiol (pg/mL) |
|---|---|---|---|
| Reproductive (early follicular) | ~3-10 | ~2-10 | ~30-150 |
| Perimenopause | highly variable, often 10-25+ and swinging | variable | swinging high and low |
| Postmenopause | often >30, frequently 40-100 | often >20 | typically <30 |
Ranges are approximate, vary by laboratory and testing method, and depend on where you are in your cycle. Use your own lab’s reference range and discuss results with a clinician.
Why a single FSH test is unreliable in your 40s
In perimenopause, FSH does not climb in a tidy line. It lurches. You can have a near-menopausal FSH one week and an entirely “normal” reproductive-range reading a fortnight later, because your ovaries are still sputtering to life intermittently and estrogen is swinging with them. A single test catches one frame of a flickering film.
This is exactly why NICE guidance (NG23) advises clinicians not to use FSH testing to diagnose perimenopause or menopause in women aged over 45 who have typical symptoms. In that age group, the diagnosis is clinical: made from your pattern of symptoms and periods, not from a blood draw. A “normal” FSH in a symptomatic 47-year-old does not rule perimenopause out.
It is a common and painful experience to be told your bloods are fine and sent home unmedicated. If that has happened to you, the result may simply have been taken on a day your ovaries were briefly active. For the wider picture on when blood work does and does not help, read our guide to blood tests for perimenopause diagnosis.
When is FSH testing actually useful?
FSH testing is genuinely useful in a handful of clear situations, chiefly when a woman is younger than expected or when another cause needs ruling out. The test earns its place when the result will change what happens next.
NICE and other bodies suggest FSH testing for women aged 40 to 45 with menopausal symptoms including a change in their menstrual cycle, and for women under 40 in whom premature or early menopause, also called primary ovarian insufficiency (POI), is suspected. In suspected POI, two raised FSH readings taken four to six weeks apart, alongside missing periods, support the diagnosis, and this matters because POI has implications for bone, heart, and fertility that warrant early treatment discussion.
FSH and LH also help when periods have stopped for reasons that are not obviously menopausal, as part of investigating absent periods (amenorrhoea) to separate ovarian causes from pituitary, thyroid, or other causes. If your symptoms could be thyroid rather than hormonal, our piece on perimenopause or thyroid explains how to tell them apart. Not sure where you sit? Yellow’s symptom quiz can help you organise what to raise with a clinician.
How does LH relate to FSH in menopause?
LH rises alongside FSH as the ovaries age, for the same reason: the feedback loop loses its “off” signal. In postmenopausal women, both gonadotrophins run high, though FSH typically climbs higher and is the more useful marker for confirming menopause.
The FSH to LH relationship can also hint at other conditions. In polycystic ovary syndrome (PCOS), for instance, LH is often relatively high compared with FSH, which is a different picture from the menopausal pattern where both are elevated but FSH leads. This is one reason clinicians interpret the two together rather than in isolation.
For most women asking about menopause, LH is a supporting actor. FSH, estradiol, your symptoms, and your period history carry the lead. If your estrogen is clearly low, our overview of low estrogen symptoms describes what that can feel like day to day.
Why can’t women on hormonal contraception use FSH testing?
Hormonal contraception makes FSH and LH testing unreliable because it deliberately suppresses them. The combined pill, and to varying degrees other hormonal methods, work in part by flattening the pituitary’s FSH and LH signals to prevent ovulation. That is the whole point of the method, and it means a blood test cannot read your underlying ovarian activity.
If you are on the combined pill, your FSH may look low or normal even if your own ovaries have largely stopped working, because the pill is doing the talking. This is why clinicians generally do not use FSH testing to assess menopause in women using combined hormonal contraception, and why age and symptoms become the better guide.
The practical question of when to stop contraception as you approach menopause is one to raise directly with a practitioner, since timing depends on your age, method, and symptoms. You can find menopause-literate clinicians through the Yellow practitioner directory on spotyellow.com.
What should you do with your FSH result?
Bring it to a clinician in context, not in isolation. A single number means little without your age, your symptom pattern, your period history, and often a repeat test. The most useful thing you can do is arrive at an appointment with a clear record of your symptoms and cycles, so the conversation is grounded in your lived experience rather than one lab value.
If you are over 45 with typical symptoms, you may not need a blood test at all, and a clinician can reasonably diagnose and discuss treatment based on how you feel. If you are under 40 to 45, or your situation is unusual, FSH and LH become far more informative. Either way, the number is a tool for a conversation, not a verdict delivered on its own.
Frequently Asked Questions
What FSH level indicates menopause?
A sustained FSH above roughly 30 mIU/mL on repeat testing, together with no periods for 12 months, indicates a menopausal pattern. Postmenopausal readings are often 40 to 100 mIU/mL. Ranges vary by laboratory, so read your result against your own lab’s reference range and with a clinician.
Can a normal FSH rule out perimenopause?
No. In your 40s, FSH swings so much that a normal reading can occur even when you are clearly perimenopausal. NICE advises diagnosing perimenopause in women over 45 from symptoms, not bloods. A normal FSH in a symptomatic woman does not rule perimenopause out, so trust your symptoms.
Why does FSH go up during menopause?
FSH rises because your ovaries have fewer responsive follicles left and produce less estrogen. The pituitary gland tries to compensate by releasing more FSH to prompt a response that no longer comes reliably. High FSH therefore reflects quiet ovaries, not a faulty pituitary gland.
Does the pill affect FSH test results?
Yes. Hormonal contraception, especially the combined pill, suppresses FSH and LH on purpose to prevent ovulation. This flattens the readings, so a blood test on the pill cannot reliably reflect your underlying ovarian activity. Clinicians generally rely on age and symptoms instead in this situation.
Should I get my FSH tested if I am over 45?
Usually not, if you have typical menopausal symptoms. NICE guidance advises a clinical diagnosis from symptoms in this age group, because FSH testing adds little and can mislead. Testing becomes more useful if you are under 45, or if another cause of your symptoms needs ruling out.
What is the difference between FSH and LH?
Both are pituitary hormones that signal the ovaries. FSH drives follicles to mature; LH triggers ovulation. Both rise as the ovaries age, but FSH climbs earlier and higher, making it the main marker for menopause. LH is usually read alongside FSH rather than on its own.
Further Reading
- NICE. Menopause: diagnosis and management (NG23). https://www.nice.org.uk/guidance/ng23
- The Menopause Society. Menopause Topics: Patient Education. https://menopause.org/patient-education/menopause-topics
- NHS. Menopause. https://www.nhs.uk/conditions/menopause/
- British Menopause Society. Tools for Clinicians. https://thebms.org.uk/publications/tools-for-clinicians/
- ACOG. Women’s Health. https://www.acog.org/womens-health
This article is for general information and is not medical advice; discuss your FSH and LH results, symptoms, and any treatment decisions, including whether testing is appropriate for you, with a qualified clinician who knows your history.