Not Ovulating: Which Cause Is Yours, and Which Test Says So

Anovulation means no egg was released in that cycle. It is a finding, not a diagnosis, and the useful question is which of a small number of causes is behind it. FIGO's 2022 Ovulatory Disorders Classification (Munro et al, Fertility and Sterility 2022) sorts every cause into four groups, remembered as HyPO-P: a problem in the hypothalamus, a problem in the pituitary, a problem in the ovary itself, or PCOS, which FIGO gave its own category because it does not sit neatly in any of the other three.

That grouping is not academic. Low body weight and heavy training are treated by restoring energy intake. A high prolactin is treated with a tablet that lowers prolactin. Anovulatory PCOS is treated with letrozole. Premature ovarian insufficiency is not treated by stimulating an ovary that has run out of follicles. The same word — anovulation — leads to four different next steps.

If you want the wider picture of how these hormones fit together first, hormones in female reproduction covers the cycle itself. This page is about telling the causes apart.

Not necessarily, and the reverse is also true: monthly bleeding is not proof that you ovulated. The 2023 International PCOS Guideline states plainly, at practice point 1.1.5, that ovulatory dysfunction can still occur with regular cycles, and that serum progesterone can be measured if anovulation needs confirming. NICE guideline NG257 takes the same position from the other side: it says regular monthly cycles make ovulation likely, and then still offers a mid-luteal progesterone to confirm it.

What counts as irregular is defined rather than felt. The 2023 guideline's recommendation 1.1.1 sets the thresholds by how long it has been since your first period.

• More than three years after menarche and before perimenopause: cycles shorter than 21 days or longer than 35 days, or fewer than eight cycles in a year.
• Between one and three years after menarche: shorter than 21 or longer than 45 days.
• Any single cycle longer than 90 days, from one year after menarche onward.
• No first period by age 15, or more than three years after breasts began developing.

In the first year after menarche, irregular cycles are normal and the guideline says so.

A mid-luteal serum progesterone. NG257 recommendation 1.18.7 puts it on day 21 of a 28-day cycle. If your cycles are long and irregular, recommendation 1.18.8 says the timing moves with the cycle — for example day 28 of a 35-day cycle — and the test is repeated weekly until the next period starts. That repetition is the part most often left out, and it is the reason a single badly timed result should not be treated as an answer.

Two things this test is not. It is not a measure of how much progesterone you make: Filicori and colleagues sampled blood every ten minutes across 24 hours in the luteal phase and found mid-luteal progesterone swinging between 2.3 and 40.1 ng/ml within minutes, in step with pulses of LH.

It is also not a test of luteal phase quality, which is a separate and much weaker claim — what a low progesterone result can and cannot show goes through the evidence on that.

NG257 recommendation 1.18.9 says not to use basal body temperature charts to confirm ovulation, because they do not reliably predict it. If you have been charting for months, the chart is not worthless as a record of your bleeding pattern, but it is not the test.

Once anovulation is confirmed, the tests that separate the groups are few and cheap. NG257 recommendation 1.18.10 offers FSH and LH to anyone with irregular cycles. Recommendation 1.18.11 says prolactin should not be offered to everyone worried about fertility, but should be offered to those with an ovulatory disorder — which, if you are reading this, is you. Recommendation 1.18.12 restricts thyroid testing to people with symptoms of thyroid disease.

• Hypothalamic. Low or normal FSH and LH with low estradiol, in the context of weight loss, low body weight, heavy training, restricted eating or sustained stress. The Endocrine Society's 2017 guideline describes functional hypothalamic amenorrhoea as a form of chronic anovulation and a diagnosis of exclusion — meaning other causes are ruled out first, not that it is a guess.
• Pituitary. A raised prolactin, sometimes with milk discharge or headaches. The Pituitary Society's 2023 consensus statement sets out how hyperprolactinaemia is confirmed and imaged before anyone treats it.
• Ovarian. A raised FSH. ESHRE's 2024 guideline diagnoses premature ovarian insufficiency on disordered cycles for at least four months plus one FSH above 25 IU/l, repeated after four to six weeks if the picture is unclear, and notes the FSH does not have to be taken on a particular cycle day.
• PCOS. Irregular cycles plus clinical or biochemical hyperandrogenism, with ultrasound or AMH only where the first two do not settle it. The 2023 guideline's recommendation 1.5.3 states that AMH should not be used as a single test to diagnose PCOS.

Thyroid disease deserves its own note because it is common in India and easily missed: see which thyroid finding actually changes treatment. For what the day-3 numbers themselves mean, FSH, LH and estradiol on a day-3 panel goes through each one.

This is the group most often mislabelled as PCOS, because both produce absent periods in a young woman. The direction of the problem is opposite. In functional hypothalamic amenorrhoea the brain has reduced its signalling because energy intake is not covering energy spent — through dieting, through training volume, or through both together, and not only in women who look underweight. The Endocrine Society's 2017 guideline treats it as a diagnosis of exclusion and calls for medical, dietary and mental health input together, not a fertility drug first.

Restoring intake and reducing training load is the treatment, and it is slower and harder than a prescription. It also addresses the bone loss the same guideline lists alongside infertility.

For anovulatory PCOS with no other infertility factor, the 2023 International PCOS Guideline is unambiguous: recommendation 5.3.1 makes letrozole the first-line pharmacological treatment for ovulation induction, and recommendation 5.4.5.1 says letrozole should be used rather than clomiphene citrate, to improve ovulation, clinical pregnancy and live birth rates. Two practice points sit alongside it: 5.3.2 notes letrozole is still off-label for this use in many countries, and 5.3.3 says it should not be given where a pregnancy might already exist.

For the other three groups the drug is different or there is no drug. A prolactinoma is treated by lowering prolactin. Premature ovarian insufficiency does not respond to ovulation induction, and the conversation there is about donor eggs and about hormone therapy for bone and heart health. Hypothalamic anovulation is treated by restoring energy balance. This is why the cause is worth establishing before a prescription rather than after.

Weight is a real factor and also an over-prescribed one. The 2023 guideline's recommendation 5.1.1 says women with PCOS should be counselled on the effect of excess weight on pregnancy and live birth after fertility treatment. But the LIFEstyle randomised trial tested putting treatment on hold for six months of lifestyle intervention in 577 women with a BMI of 29 or above, and the delayed group had fewer healthy term births, not more: 27.1% versus 35.2% for prompt treatment, a rate ratio of 0.77 with a confidence interval of 0.60 to 0.99. That is an argument against delay, not an argument against weight loss.

Do not stop a prescribed medicine on the strength of a web page. Clomiphene citrate works, and the 2023 guideline still lists uses for it, including in preference to metformin alone (recommendation 5.4.2.1) and combined with metformin. What the guideline says is that letrozole works better as a first choice in PCOS. If you are already responding and ovulating on clomiphene, that is the outcome you wanted.

The reasonable question at your next appointment is whether letrozole was considered, and whether the cause of your anovulation was established before the drug was chosen. There is more on clomiphene specifically in where clomiphene works and where it does not.

Several things this page cannot tell you, and neither can anyone who has not tested you.

• Whether an occasional anovulatory cycle in an otherwise regular pattern reduces your chance of pregnancy over a year. That has not been quantified in the guidance cited here.
• How long after correcting a thyroid abnormality or a raised prolactin ovulation returns. NG257 restricts who should be tested; it does not give a recovery timeline.
• Whether acupuncture or any supplement restores ovulation. The 2023 PCOS guideline's recommendation 4.7.1 says inositol could be considered on individual preference while noting limited clinical benefit including in ovulation; no guidance cited here supports acupuncture.
• Whether AMH predicts your chance of conceiving naturally. NG257 recommendation 1.18.3 says not to use AMH as a predictor of clinical pregnancy through spontaneous conception.
• What your own FSH, prolactin or progesterone results mean, which depends on when in the cycle they were drawn and which assay the laboratory used.

Not ovulating is one of the more treatable reasons for not conceiving, which is worth saying out loud after a paragraph of caveats. The work is in finding out which cause it is.