--- title: "FSH vs LH: What Each Hormone Does, How the Two Tests Differ, and How to Read Them Together" type: guide url: "https://www.test-well.com/guides/fsh-vs-lh" date_published: 2026-09-28 reviewed_at: 2026-09-28 --- # FSH vs LH: What Each Hormone Does, How the Two Tests Differ, and How to Read Them Together *Two pituitary hormones, released together, measured together — and almost never interpreted alone. FSH grows the egg or sperm; LH triggers ovulation and drives testosterone. The relationship between them is what the tests are really for.* > FSH (follicle-stimulating hormone) and LH (luteinizing hormone) are both made by the pituitary and both act on the ovaries or testes, but they do different jobs: FSH recruits and matures the egg follicle (or supports sperm production), while LH triggers ovulation and drives progesterone in women and testosterone in men. They are ordered together because the pattern — both high, both low, or LH higher than FSH — points to the cause of irregular cycles, infertility, low testosterone or menopause far better than either value alone. For a baseline, draw them on cycle day 2–4. ## Recommended tests | Recommended | Type | Price | Why | | --- | --- | --- | --- | | [FSH (Follicle Stimulating Hormone)](https://www.test-well.com/tests/fsh) | Test | $29.99 | Follicle-stimulating hormone — ovarian reserve and menopause signal | | [LH (Luteinizing Hormone)](https://www.test-well.com/tests/luteinizing-hormone) | Test | $36.99 | Luteinizing hormone — ovulation trigger, PCOS pattern, testicular drive | | [Women's Hormone Panel](https://www.test-well.com/tests/womens-hormone-panel) | Panel (11 tests) | $239.99 | FSH, LH, estradiol, progesterone and more in one draw | | [Men's Hormone Panel](https://www.test-well.com/tests/mens-hormone-panel) | Panel (7 tests) | $199.99 | FSH and LH with total and free testosterone for men | All prices are cash-pay plus one $6 lab processing fee per order; physician authorization is included. ## The One-Paragraph Answer The pituitary gland sits at the base of the brain and steers the ovaries and testes with two hormones. **FSH** tells the ovary to grow a follicle each cycle (and tells the testes to make sperm). **LH** delivers the surge that makes that follicle release its egg, then keeps the resulting corpus luteum producing progesterone; in men, LH tells the Leydig cells of the testes to make testosterone. When the ovaries or testes underperform, the pituitary pushes harder and both hormones rise. When the problem is upstream — in the pituitary or hypothalamus — both fall. And in a few conditions the two diverge, which is a clue in itself. ## What the FSH Test Measures FSH is reported in mIU/mL. In women it is low in the early cycle, rises modestly as a follicle is selected, spikes briefly with LH at ovulation, and falls in the luteal phase. Its most-used reading is the **day 2–4 baseline**: a rising early-cycle FSH means the ovary needs more stimulation to produce a follicle, which is the classic marker of declining ovarian reserve. After menopause FSH stays persistently high — often above 25–40 mIU/mL — because there are no follicles left to respond. In men FSH supports sperm production, so it is measured in infertility evaluations: a high FSH with a low sperm count points to a problem in the testes themselves. For ovarian-reserve questions in women, guidelines note that **AMH** is a steadier marker than FSH because it does not swing with the cycle; the two are often ordered together. The [FSH reference page](https://www.test-well.com/biomarkers/fsh) lists the phase-specific ranges. ## What the LH Test Measures LH is also reported in mIU/mL and moves more dramatically than FSH. In women it sits low for most of the cycle and then surges to several times its baseline for about a day, roughly 24–36 hours before ovulation — the surge that ovulation predictor kits detect in urine. In the luteal phase it supports progesterone production. After menopause it is persistently high, like FSH. LH's special value is in two patterns. In **polycystic ovary syndrome**, LH often runs high relative to FSH (a ratio above about 2:1 is a common, though not diagnostic, finding), which supports the diagnosis alongside irregular cycles, androgen excess and ultrasound findings. In **men**, LH is the number that says where low testosterone is coming from: high LH with low testosterone means the testes are not responding (primary hypogonadism); low or normal LH with low testosterone means the pituitary is not sending the signal (secondary hypogonadism), which changes the work-up entirely. The [LH reference page](https://www.test-well.com/biomarkers/lh) has the ranges. ## FSH vs LH: Side by Side | | FSH | LH | | --- | --- | --- | | Made by | Pituitary | Pituitary | | Main job (women) | Recruits and matures the follicle | Triggers ovulation; supports progesterone | | Main job (men) | Supports sperm production | Drives testosterone production | | Cycle pattern | Modest rise early, small peak at ovulation | Low, then a sharp mid-cycle surge | | Signature use | Ovarian reserve (day 2–4); menopause confirmation; testicular failure in men | Ovulation timing; PCOS pattern (LH > FSH); locating the cause of low testosterone | | After menopause | Persistently high | Persistently high | | Best drawn | Cycle day 2–4 for baseline | Same draw as FSH; mid-cycle only if timing ovulation | | Fasting | No | No | ## Which Should You Order? Almost always both, from the same draw — the cost difference is small and the pattern is the point. The question is really what else to add: - **Irregular or absent periods:** FSH and LH with estradiol, prolactin and TSH — the standard first set, which separates PCOS, ovarian insufficiency, pituitary causes and thyroid disease. The [Women's Hormone Panel](https://www.test-well.com/tests/womens-hormone-panel) covers it. - **Fertility planning or trying to conceive:** day 2–4 FSH, LH and estradiol, plus AMH for reserve; mid-luteal progesterone if you want to confirm ovulation. The [Women's Fertility Essentials](https://www.test-well.com/tests/female-fertility-panel) panel is built around this. - **Perimenopause or menopause questions:** FSH with estradiol. A persistently high FSH with low estradiol fits menopause, but in women over 45 guidelines diagnose on symptoms and age; a single value during perimenopause can be misleading because levels swing. - **Low testosterone in men:** FSH and LH alongside total and (calculated) free testosterone, drawn in the morning — the LH result decides whether the problem is the testes or the pituitary. The [Men's Hormone Panel](https://www.test-well.com/tests/mens-hormone-panel) pairs them. - **Male infertility:** FSH, LH and testosterone with a semen analysis arranged separately. ## How to Read FSH and LH Together | FSH | LH | Context | Usual meaning | | --- | --- | --- | --- | | High | High | Woman, low estradiol | Ovaries not responding — menopause, or primary ovarian insufficiency if under 40. Confirm with a repeat 4–6 weeks later. | | Normal | High (LH:FSH above ~2:1) | Woman, irregular cycles, androgen excess | Pattern consistent with PCOS — supportive, not diagnostic; the diagnosis rests on cycles, androgens and ultrasound. | | Low | Low | Woman, low estradiol, no periods | Upstream (hypothalamic or pituitary) cause — low body weight, heavy training, stress, high prolactin, thyroid disease, or a pituitary problem. Prolactin, TSH and sometimes imaging follow. | | Rising day-3 FSH | Normal | Woman, regular cycles | Declining ovarian reserve; AMH adds precision. It predicts response to fertility treatment more than the chance of natural conception. | | High | High | Man, low testosterone | Primary hypogonadism — the testes are not responding; causes include Klinefelter syndrome, prior injury, chemotherapy or radiation, mumps orchitis. | | Low or normal | Low or normal | Man, low testosterone | Secondary hypogonadism — the pituitary signal is weak; obesity, opioids, high prolactin, pituitary disease and exogenous testosterone or steroids are the common causes. Prolactin and iron studies are typical next tests. | Neither hormone requires fasting. Cycle day is everything for women — note it on the report, and never compare a mid-cycle LH surge with a day-3 baseline. Hormonal contraception suppresses both, so results while on it reflect the contraceptive. For men, draw in the morning with testosterone. ## What to Do With the Result The FSH/LH pattern narrows the cause; the next tests confirm it. High-high in a woman under 40 is repeated and, if persistent, evaluated for primary ovarian insufficiency, which has implications for bone and heart health beyond fertility. The PCOS pattern is completed with androgens, glucose and lipid testing, since PCOS carries metabolic risk. Low-low is worked up with prolactin, TSH and a history of weight, training and stress; a pituitary MRI follows if prolactin is high or other pituitary hormones are off. In men, high LH prompts a testicular evaluation and often a karyotype; low LH prompts prolactin, iron studies and a medication review before any testosterone therapy is considered — because treating secondary hypogonadism with testosterone without finding the cause can miss a pituitary problem and suppresses fertility. FSH and LH are routine draws at Quest and Labcorp, orderable through TestWell with physician review, results in a few business days with cycle-phase reference ranges on the report. ## Frequently asked questions ### What is the difference between FSH and LH? Both come from the pituitary, but FSH matures the egg follicle (and supports sperm production) while LH triggers ovulation and drives progesterone in women and testosterone in men. FSH is the ovarian-reserve and menopause marker; LH is the ovulation-timing marker, the PCOS pattern hormone, and the number that locates the cause of low testosterone in men. ### Should FSH and LH be tested together? Yes — the relationship between them is the useful information. Both high with low estradiol fits menopause or ovarian insufficiency; LH higher than FSH fits PCOS; both low points to a pituitary or hypothalamic cause; and in men, high LH with low testosterone means a testicular problem while low LH means a pituitary one. ### What day of my cycle should I test FSH and LH? Cycle day 2–4 for a baseline, ideally with estradiol. Mid-cycle draws are only for timing the LH surge before ovulation. Always note the day on the report — an LH surge value looks alarming next to a day-3 reference range but is completely normal on day 13. ### What FSH level indicates menopause? Persistently elevated FSH — often above 25–40 mIU/mL — with low estradiol and no periods for a year fits menopause, but levels swing during perimenopause and a single value can mislead. In women over 45, guidelines base the diagnosis on age and symptoms, not on FSH. ### What does a high LH to FSH ratio mean? An LH:FSH ratio above about 2:1 in a woman with irregular cycles and signs of androgen excess is a pattern often seen in PCOS. It supports the diagnosis but is not required for it or diagnostic on its own — many women with PCOS have a normal ratio, and the diagnosis rests on cycle history, androgen levels and ultrasound. ### Why are FSH and LH checked in men with low testosterone? To find out where the problem is. High LH and FSH with low testosterone mean the testes are not responding (primary hypogonadism). Low or normal LH with low testosterone means the pituitary is not signalling enough (secondary hypogonadism), which points to causes like obesity, opioids, high prolactin or pituitary disease and changes the work-up before any treatment. ## Sources - [Practice Committee of the American Society for Reproductive Medicine. Testing and interpreting measures of ovarian reserve: a committee opinion. Fertil Steril 2020;114:1151–1157.](https://doi.org/10.1016/j.fertnstert.2020.09.134) - [Teede HJ, et al. International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome 2023. J Clin Endocrinol Metab 2023;108:2447–2469.](https://doi.org/10.1210/clinem/dgad463) - [Bhasin S, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 2018;103:1715–1744.](https://doi.org/10.1210/jc.2018-00229) - [MedlinePlus (NIH) — FSH Levels Test; Luteinizing Hormone (LH) Levels Test](https://medlineplus.gov/lab-tests/follicle-stimulating-hormone-fsh-levels-test/) --- Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-09-28. Review policy: https://www.test-well.com/reviewers/youmna-distefano-md Canonical page: https://www.test-well.com/guides/fsh-vs-lh Machine-readable catalog: https://www.test-well.com/api/catalog.json · MCP server: https://www.test-well.com/mcp · Overview for agents: https://www.test-well.com/llms.txt Prices are cash-pay, in USD, and include physician authorization; every order adds one flat $6 lab processing fee. Educational content is not a diagnosis — discuss results with a clinician.