Melatonin for PCOS: Sleep, Ovarian Function and the Honest Evidence Grade

Does melatonin actually help PCOS?

Melatonin raised total antioxidant capacity by a standardized mean difference of 0.87 in a 2024 meta-analysis pooling 6 randomized trials, the single most consistent finding in the entire melatonin-PCOS literature (Ziaei et al., 2024). A larger 2025 meta-analysis of 12 trials and 1,590 women confirmed the antioxidant effect and additionally found melatonin improved endometrial thickness and clinical pregnancy rate (SMD 0.97 for the combined endometrial-thickness measure) (Shoarishoar et al., 2025). Both reviews stop short of calling melatonin a proven treatment for the cardiometabolic and hormonal problems PCOS actually causes — they call for larger, longer trials before drawing that conclusion.

What dose was actually used in the trials, and for how long?

Six mg per day, split as two 3 mg tablets, is the dose that produced the sleep and hormone changes in the best-designed PCOS-specific trial: 84 women took melatonin alone, magnesium alone, both combined, or placebo for 8 weeks (Alizadeh et al., 2021). Across the wider trial pool, doses varied far more than that one number suggests — the 2024 meta-analysis found doses of 3 to 10 mg/day across its 6 studies, while the larger 2025 meta-analysis found a much wider spread of 1.8 to 100 mg/day across 12 studies, with an average follow-up of about 11 weeks. That is a 54-fold range in dose across pooled trials, which is a bigger source of inconsistency in this literature than any single result table can show — a specific study result does not automatically apply at a different dose. It is also a wide gap from what is on a typical pharmacy shelf: most over-the-counter melatonin products sell 0.5 to 5 mg tablets, well below the middle and upper end of the trial range, and next-day grogginess and slowed reaction time are dose-related effects of melatonin generally — a consideration for driving or operating machinery the next morning that becomes more relevant the closer a dose sits to the higher end of what trials have used.

Does melatonin actually improve sleep quality in PCOS?

Yes, in the one trial that measured it directly: Pittsburgh Sleep Quality Index scores dropped significantly (P<0.001) in both the melatonin-alone group and the melatonin-plus-magnesium group after 8 weeks, while the magnesium-only and placebo groups did not improve to the same degree (Alizadeh et al., 2021). This is a real, PCOS-specific result — not an extrapolation from general-population insomnia research — but it comes from one trial of 84 women, not a replicated body of evidence. PCOS carries a documented higher rate of poor sleep and sleep apnoea; see the fuller picture in PCOS and sleep if disrupted sleep, not oxidative stress or hormones, is your main reason for reading this page.

Does melatonin lower testosterone or help with hormonal symptoms?

Testosterone fell significantly only in the group taking melatonin combined with magnesium, not in the group taking melatonin alone, in the same 8-week trial (Alizadeh et al., 2021). A companion analysis of the same 84 women found the melatonin-magnesium combination also reduced hirsutism scores more than either supplement alone or placebo, and lowered the inflammatory marker TNF-α, while melatonin by itself independently reduced TNF-α without magnesium (Mousavi et al., 2022). The pattern across both papers is consistent: melatonin alone moves antioxidant and inflammatory markers; the combination with magnesium is what moved testosterone and hirsutism. If androgen symptoms are your target, the trial evidence supports the combination, not melatonin in isolation — see magnesium for PCOS for that supplement’s evidence on its own.

Does melatonin help ovarian function or pregnancy outcomes?

A randomized trial of 198 women with PCOS undergoing intrauterine insemination found melatonin (3 mg/day from cycle day 3 to the hCG trigger) produced a chemical pregnancy rate of 32%, compared with 18% on placebo, and significantly improved endometrial thickness (Mokhtari et al., 2019). The larger 2025 meta-analysis found the same direction of effect on endometrial thickness and pregnancy rate across its pooled data. This is real trial evidence, and it is also a single population undergoing a specific fertility procedure — it describes what one trial measured, not a treatment sequence to bring to a fertility appointment or a reason to delay a referral if you are already trying to conceive.

What about inositol and sleep?

No trial has tested myo-inositol for sleep quality in women with PCOS. The closest available evidence comes from a different population entirely: a randomized trial of 60 pregnant women (not PCOS) found 2,000 mg/day of myo-inositol for 10 weeks significantly improved global sleep quality, subjective sleep quality, and sleep duration on the same PSQI scale used in the PCOS melatonin trial (Mashayekh-Amiri et al., 2022). That is a plausible signal worth knowing about, not PCOS evidence — say so plainly rather than borrowing it as if it were.

Who is this wrong for?

If you are hoping melatonin will resolve cardiometabolic risk broadly — cholesterol, blood pressure, or long-term weight trajectory — the meta-analyses reviewed here explicitly say the evidence does not support that yet; the antioxidant effect is the one finding both reviews agree on. If you already take a sedating medication, a sleep aid, or a benzodiazepine, adding melatonin without medical guidance risks compounding daytime drowsiness rather than adding a distinct benefit. And if your main goal is androgen-symptom relief, the only trial that showed a testosterone effect used melatonin paired with magnesium, not melatonin by itself — expecting the same result from melatonin alone extrapolates beyond what was tested.

You may see PCOS referred to as polyendocrine metabolic ovarian syndrome (PMOS) after a 2026 global consensus of more than 50 organisations renamed it. Nothing about the melatonin evidence above changed with the name — this article uses PCOS because that is still what readers search.

If insulin resistance rather than sleep is your priority, alpha-lipoic acid has a more direct trial evidence base for that specific marker, and the probiotics evidence is graded separately for anyone comparing gut-focused options in the supplements section. Shopping for a sleep product specifically rather than melatonin on its own? Our review of PCOS sleep supplements checks what else is actually in them.

Common questions