Free tool

LH to FSH Ratio Calculator

Q: What is a normal LH to FSH ratio?

In the early follicular phase (cycle day 2–4) FSH is usually at or slightly above LH, so a ratio around 1 or below is the expected pattern. There is no single cut-off that defines normal; the ratio is read alongside the absolute LH and FSH values and the cycle day.

Q: Does an LH:FSH ratio above 2 mean I have PCOS?

Not by itself. An LH-predominant ratio is common in PCOS, but the Rotterdam criteria and the 2023 international guideline diagnose PCOS from irregular ovulation, clinical or biochemical hyperandrogenism and ovarian morphology or AMH — the ratio is supporting information. A ratio above 2 drawn near ovulation is also just the LH surge.

Q: Why does the cycle day matter so much?

LH rises several-fold for a day or two around ovulation, which flips the ratio in a woman with completely normal hormones. Day 2–4 of the cycle is the standard window because both hormones are at baseline. Hormonal contraception, pregnancy and breastfeeding also change both values.

Q: Does the LH:FSH ratio apply to men?

Not as a standard measure. In men, LH and FSH are interpreted individually against total testosterone: high LH with a low testosterone points to a testicular (primary) cause, low or normal LH with a low testosterone to a pituitary or hypothalamic (secondary) cause, per the Endocrine Society guideline.

The short answer

Enter LH and FSH from the same cycle day 2–4 draw and the calculator divides them to give the LH:FSH ratio. In that window FSH normally sits at or a little above LH, so a ratio of about 1 or below is usual. A ratio of 2 or more is common in PCOS but is not a diagnostic criterion, and a sample near the mid-cycle LH surge inverts the ratio.

Inputs: LH · FSH (same draw)
When to draw: Cycle day 2–4
Usual early-follicular: ratio ≈ 1 or below
Cost: Free

LH (luteinizing hormone)

mIU/mL

Cycle day 2–4 for a cycling woman; mIU/mL = IU/L · LH range

FSH (follicle-stimulating hormone)

mIU/mL

Same draw as the LH · FSH range

Enter your values to calculate.

LH:FSH = LH [mIU/mL] ÷ FSH [mIU/mL] from the same sample (both in the same units, so the ratio has none)

Educational — a derived index, not a diagnosis. Nothing you enter leaves your browser.

How the LH:FSH ratio is calculated

LH:FSH = LH [mIU/mL] ÷ FSH [mIU/mL] from the same sample (both in the same units, so the ratio has none)

Worked example

LH (luteinizing hormone) (mIU/mL)	FSH (follicle-stimulating hormone) (mIU/mL)	LH:FSH ratio
12	5	2.40

FSH:LH (the inverse): 0.42

Falls in: LH-predominant.

How to read the result

LH:FSH ratio	Reads as	What it usually means
< 1	FSH higher than LH	In the early follicular phase (cycle day 2–4) FSH is normally at or a little above LH, so a ratio under 1 is the expected pattern in a cycling woman. When FSH is high in absolute terms as well, the ratio reflects the shift toward perimenopause or diminished ovarian reserve — read the FSH value itself, with estradiol and AMH, rather than the ratio.
1 – 2	Roughly balanced	LH and FSH within a factor of two of each other is common in healthy early-follicular samples and carries no particular signal on its own.
2 – 3	LH-predominant	A ratio of 2 or more is seen in a large share of women with polycystic ovary syndrome, but it is not a diagnostic criterion: the Rotterdam and 2023 international PCOS guideline criteria rest on ovulatory dysfunction, clinical or biochemical hyperandrogenism and ovarian morphology or AMH, not the ratio. Confirm the sample was drawn on day 2–4 and not around ovulation.
≥ 3	Strongly LH-predominant	The classic PCOS pattern when drawn in the early follicular phase — and also what a sample drawn near the mid-cycle LH surge looks like, because LH rises several-fold for a day or two. Check the cycle day first; if the timing was right, a clinician will interpret it with testosterone, SHBG, AMH and the cycle history.

Cut points reviewed by Youmna DiStefano, MD on 2026-10-09. Sources below.

Limits

The ratio is only interpretable in a cycling woman sampled on cycle day 2–4 who is not using hormonal contraception; the mid-cycle LH surge, pregnancy, breastfeeding, hormonal contraception and the menopausal transition all change it. In men the LH:FSH ratio is not a standard measure — LH and FSH are read individually against total testosterone to separate testicular from pituitary causes of a low level. It supports, and never replaces, the criteria clinicians use for PCOS or ovarian reserve.

Sources

Rotterdam ESHRE/ASRM-Sponsored PCOS Consensus Workshop Group. Revised 2003 consensus on diagnostic criteria and long-term health risks related to polycystic ovary syndrome. Hum Reprod 2004;19:41–47. doi.org/10.1093/humrep/deh098
Teede HJ, et al. Recommendations from the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. J Clin Endocrinol Metab 2023;108:2447–2469. doi.org/10.1210/clinem/dgad463
Harlow SD, et al. Executive summary of the Stages of Reproductive Aging Workshop + 10 (STRAW+10). J Clin Endocrinol Metab 2012;97:1159–1168. doi.org/10.1210/jc.2011-3362
Bhasin S, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 2018;103:1715–1744. doi.org/10.1210/jc.2018-00229

Frequently asked questions

What is a normal LH to FSH ratio?

In the early follicular phase (cycle day 2–4) FSH is usually at or slightly above LH, so a ratio around 1 or below is the expected pattern. There is no single cut-off that defines normal; the ratio is read alongside the absolute LH and FSH values and the cycle day.

Does an LH:FSH ratio above 2 mean I have PCOS?

Not by itself. An LH-predominant ratio is common in PCOS, but the Rotterdam criteria and the 2023 international guideline diagnose PCOS from irregular ovulation, clinical or biochemical hyperandrogenism and ovarian morphology or AMH — the ratio is supporting information. A ratio above 2 drawn near ovulation is also just the LH surge.

Why does the cycle day matter so much?

LH rises several-fold for a day or two around ovulation, which flips the ratio in a woman with completely normal hormones. Day 2–4 of the cycle is the standard window because both hormones are at baseline. Hormonal contraception, pregnancy and breastfeeding also change both values.

Does the LH:FSH ratio apply to men?

Not as a standard measure. In men, LH and FSH are interpreted individually against total testosterone: high LH with a low testosterone points to a testicular (primary) cause, low or normal LH with a low testosterone to a pituitary or hypothalamic (secondary) cause, per the Endocrine Society guideline.

Which biomarkers does this tool cover?

Which tests give you these numbers?

Physician-authorized, drawn at Quest, Labcorp or BioReference. Results in 1–3 business days for most tests.