What do FSH and LH levels mean? Reference ranges by cycle day and age.
FSH and LH are the two pituitary hormones that drive your cycle. Measured on day 2 to 3, both usually sit in the low single digits to about 10 IU/L. A high FSH can point to reduced ovarian response or the menopause transition; a low FSH or LH can point to a suppressed signal from the brain. The day you test changes everything.
What FSH and LH do across the cycle
Follicle-stimulating hormone (FSH) and luteinising hormone (LH) are released by the pituitary gland at the base of your brain. Between them they run the conversation between your brain and your ovaries. (Also searched as "luteinizing hormone"; it is the same hormone.)
Early in the cycle, FSH stimulates a group of small follicles in the ovary to start growing. One takes the lead and produces oestradiol. As oestradiol rises, it signals the brain to ease off FSH, so only the lead follicle keeps going.
When oestradiol peaks, the brain responds with a sharp surge of LH, which triggers ovulation within about 24 to 36 hours. The empty follicle then becomes the corpus luteum and makes progesterone for the second half of the cycle, while FSH and LH fall back to baseline.
So both hormones are quiet through the luteal phase and peak around ovulation, which is why a single result only makes sense once you know which day it was taken on.
Reference ranges on day 2 to 3
Baseline readings are taken on day 2 to 3, and no later than day 5, counting the first day of full bleeding as day 1. The figures below are typical for a woman with regular cycles who is not using hormonal contraception.
| Marker | Typical early-cycle range | What it usually means |
|---|---|---|
| FSH (day 2 to 3) | About 3 to 10 IU/L | The ovaries are responding readily to a normal signal from the brain. Readings above about 10 to 12 IU/L are read more carefully, especially with a low oestradiol. |
| LH (day 2 to 3) | About 2 to 10 IU/L | A quiet baseline. LH climbs steeply only around the mid-cycle surge, when it can reach several times this level for a day or two. |
| Oestradiol (day 2 to 3) | About 100 to 400 pmol/L | Low and steady at the start of the cycle. It is read alongside FSH, because a high oestradiol can mask a rising FSH. |
| FSH after menopause | Usually above about 25 to 30 IU/L | Persistently high FSH with low oestradiol and no periods for 12 months is the hormone picture of menopause. |
Ranges vary by laboratory; your report shows the range your lab uses. Typical ranges on this page are drawn from Pathology Tests Explained (RCPA) and the sources listed below.
There is no agreed "FSH by age" table in the way there is for AMH, because FSH is far more variable from month to month. What changes with age is how often an early-cycle FSH sits above the usual range, which becomes more common through the late thirties and forties.
What a high FSH can indicate
A raised early-cycle FSH means the brain is sending a stronger signal to get the ovaries to respond. There are three common reasons.
- Declining ovarian reserve. As the pool of small follicles shrinks, the ovaries make less of the hormones that would normally hold FSH down. FSH drifts upward, at first only in some cycles and then more consistently. FSH is a less stable marker of ovarian reserve than AMH, so the two are usually read together.
- Perimenopause and menopause. During perimenopause FSH can be high one month and normal the next, which is why a single FSH cannot confirm or rule out the transition. A persistently high FSH with low oestradiol, in a woman who has not had a period for 12 months, fits menopause. In women over 45 with typical symptoms, Australasian Menopause Society guidance says testing is not needed to make that call; it is made on symptoms and cycle history.
- Timing errors. FSH rises again around ovulation, so a sample taken on day 12 of a short cycle can look "high" for no reason other than the surge. If bleeding was spotting rather than a true period, "day 3" might be nothing of the sort. Before anyone worries about a high FSH, the first question is: which day was it really?
Less commonly, a high FSH at a young age can reflect primary ovarian insufficiency, when the ovaries slow down before 40. An unexpected result in a younger woman is repeated and investigated rather than assumed.
What a low FSH or LH can indicate
Low FSH and LH together usually mean the signal from the brain is turned down, rather than anything being wrong with the ovaries. The ovaries may be perfectly capable; they are simply not being asked to work. The common causes are everyday ones:
- Significant or prolonged stress
- Under-eating or rapid weight loss
- Very high training loads, particularly in endurance sport
- Recent hormonal contraception (the effect is by design, see below)
- Pregnancy and breastfeeding
- A raised prolactin, which dampens FSH and LH release
- Less often, a pituitary condition, which your doctor considers if nothing else explains the picture
Because low FSH and LH so often go with light, irregular or absent periods, they are usually checked alongside prolactin and TSH, since thyroid problems and high prolactin can produce the same cycle changes. A low reading is rarely alarming on its own; what matters is the cause.
LH to FSH ratio and PCOS: what it can and cannot show
In many women with polycystic ovary syndrome (PCOS), baseline LH runs higher than FSH, so the LH to FSH ratio is raised. Historically a ratio above about 2 was treated as a clue to PCOS. It remains a clue, and no more than that.
If PCOS is the question, the more informative markers are testosterone, SHBG and the free androgen index. The PCOS and your hormones article explains how those fit together.
Why the day of your cycle changes the answer
Imagine three blood tests from the same woman in one month. On day 3, her FSH is 6 and her LH is 5. On day 14, at the surge, her LH is 45 and her FSH has doubled. On day 21, both are back near baseline. All three are normal for the day they were taken.
That is why KnowLuna asks you to collect on day 2 to 5 for the fertility and hormone panels: it puts your result on the same footing as the reference range. The "day 3" hormone test article goes into the practicalities of timing, including what to do if day 3 lands on a weekend.
If your cycles are irregular or you are not sure when day 1 was, the test is still worth doing. Note your last period date and tell your doctor. An untimed result is harder to read, not useless.
Contraception and FSH and LH readings
The combined pill, the vaginal ring and the contraceptive injection work partly by suppressing FSH and LH. Progestogen-only methods, such as the implant, the hormonal IUD and the mini pill, have a smaller and less predictable effect on them. So a baseline taken while you are using hormonal contraception mostly reflects the contraception, not your own ovarian function.
Low readings on the pill are expected and mean very little. Even the pill-free week is not a clean window, because the suppression does not fully lift in a few days. TSH and prolactin remain informative, though prolactin can be mildly raised. Testosterone and SHBG are not: combined hormonal contraception raises SHBG two- to four-fold and lowers free testosterone, so androgen testing is best done after about three months off it. AMH is affected less, although combined methods still lower it somewhat. If you want a true baseline, most doctors suggest waiting for one or two natural cycles off hormonal contraception. The contraception and hormone tests article covers each method in turn.
Which KnowLuna panels include FSH and LH
FSH and LH are in every KnowLuna cycle-hormone panel, always alongside oestradiol so the three can be read as a set.
- Thinking about fertility now or later: the AMH and fertility panel adds AMH, TSH and prolactin. Test-only price $179, or $259 with a KnowLuna doctor to request and explain it.
- Irregular, heavy, painful or changing cycles: the female hormone panel adds progesterone, testosterone, SHBG, prolactin, DHEA-S and cortisol.
- Changes in your forties or fifties: the perimenopause and menopause panel reads FSH, LH and oestradiol together with thyroid and iron, because those mimic the transition so often.
- PCOS in question: the PCOS panel pairs FSH and LH with androgens and fasting metabolic markers.
Any abnormal result is followed up by an AHPRA-registered doctor. Browse all fertility tests on the fertility stage page, or the cycles and hormones stage page if your question is about periods.
Common questions
What do LH and FSH levels tell you?
Read together on day 2 to 3, they show how hard your brain is working to get your ovaries to respond. A high FSH can point to declining ovarian reserve or the menopause transition; low FSH and LH can point to stress, under-eating, contraception or a raised prolactin. Neither is read alone.
What is a normal LH level for a woman?
On day 2 to 3 of the cycle, LH is usually in the low single digits to about 10 IU/L. Around ovulation it surges to several times that for a day or two, then falls back. After menopause it stays raised. Your report shows the range your lab applied.
What FSH level indicates menopause?
A persistently high FSH, typically above about 30 IU/L, with a low oestradiol and no period for 12 months fits menopause. One high reading does not confirm it, because FSH swings widely in perimenopause. In women over 45 with typical symptoms, Australasian Menopause Society guidance is that no blood test is needed.
What happens when LH is low?
Low LH usually goes with low FSH and means the brain is sending a quieter signal to the ovaries. Common reasons include hormonal contraception, significant stress, under-eating, heavy training, breastfeeding or a raised prolactin. Your doctor looks for the cause.
Are FSH and LH tests covered by Medicare?
When a GP or specialist requests them for a clinical reason, FSH and LH are often bulk-billed or attract a Medicare rebate. KnowLuna is self-pay, with no Medicare rebate: you choose the panel, collect at an accredited centre or with a home kit or a nurse visit, and receive a plain-English report, with a doctor to request and explain it if you want one.
What is the difference between FSH and TSH?
Both come from the pituitary gland, but they talk to different organs. FSH acts on the ovaries and drives egg development; TSH acts on the thyroid and sets your metabolic rate. They are often tested together because a thyroid problem can disrupt cycles in ways that look hormonal.
Sources and further reading
- Pathology Tests Explained (RCPA): follicle stimulating hormone (FSH)
- Pathology Tests Explained (RCPA): luteinising hormone (LH)
- Pathology Tests Explained (RCPA): oestradiol
- Australasian Menopause Society: Diagnosing menopause (information sheet)
- Healthdirect: follicle stimulating hormone (FSH)
- Better Health Channel: menstrual cycle
General information only, not medical advice. If your symptoms are severe or sudden, see a doctor promptly. This page does not replace a consultation with a doctor who knows your history; read our medical disclaimer.