Melatonin for Endometriosis Pain: What the Dienogest Trial Adds

Melatonin is sold for sleep, but researchers have also tested it for endometriosis pain. Those are separate treatment questions. Before adding it, identify whether the intended target is menstrual cramps, pain between periods, painful sex or poor sleep.

The dienogest study tested an addition to hormonal treatment

A 2026 trial¹ randomized 94 women with ultrasound-confirmed ovarian endometriomas. Both groups took dienogest 2 mg daily; one added melatonin 10 mg nightly, the other placebo, for six months. Deep infiltrating endometriosis was excluded.¹

Only 52 women completed the protocol. An analysis including all 94, using imputed missing data, estimated 1.2 points more improvement in menstrual pain with melatonin. Other pain measures and quality of life did not improve significantly more than with dienogest alone.¹

The adverse-event table, covering 26 completers per group, reports vertigo in 14 of 26 melatonin users versus 2 of 26 controls. Losing nearly half the participants makes interpretation difficult. This trial did not test melatonin alone or establish that it could replace dienogest.¹

Ask the clinician to weigh the particular pain outcome against the tolerability findings, rather than treating the study’s favorable title as the whole result.

An early positive trial was small

In 2013, Schwertner² and colleagues randomized 40 women aged 18 to 45 to melatonin 10 mg or placebo for eight weeks. The published abstract reports roughly 39.8% lower daily pain and 38% lower menstrual-pain scores compared with placebo, along with better sleep quality and less analgesic use.²

Those figures concern pain scores in a small trial. They are not percentages of women cured, and the study does not establish a lasting benefit after treatment ends. An eight-week pain result also cannot tell someone whether future surgery will be needed or fertility will improve.²

A higher dose failed to show a clear benefit

A Swedish 2023 trial³ randomized 40 women to 20 mg melatonin nightly or placebo for two cycles or months; 34 completed treatment. Usual pain medicines continued, and some participants also used hormonal treatment. Adjusted average pain scores were 2.9 with melatonin and 3.3 with placebo, without a statistically significant difference.³

The researchers found no significant advantage for sleep, quality of life or analgesic use either. They acknowledged that the trial could be underpowered because pain scores varied more than expected. A negative small trial does not exclude every possible benefit, but it gives no basis for assuming that doubling the dose improves pain relief.³

Another recent report separates pain from cyst size

A trial reported in the January 2026 issue of Heliyon⁴ randomized 98 women to melatonin 10 mg or placebo for eight weeks. Its abstract reports a menstrual-pain benefit but no significant effect on endometrioma size.⁴

That is an important distinction when discussing claims that a supplement “shrinks endometriosis.” A symptom result and a cyst measurement answer different questions. This report also used a different regimen from the six-month dienogest combination, so its result cannot be substituted for that comparison.⁴

Check the product and medicines before considering a trial

The US National Center for Complementary and Integrative Health⁵ describes melatonin as a hormone, with possible adverse effects including sleepiness, dizziness, headache and nausea. Long-term supplement safety remains insufficiently studied. People taking blood thinners or living with epilepsy need medical supervision; safety research in pregnancy and breastfeeding is lacking.⁵

US melatonin supplements are regulated differently from prescription medicines, and some products contain amounts that differ from their labels. Bring the actual bottle, dose per tablet and full medication list to the pharmacist or prescriber. Do not assume that a bedtime gummy reproduces a trial preparation.⁵

For the sleep-specific question, see what melatonin studies show for sleep.

Give the review appointment a symptom to measure

The NHS⁶ advises assessment when suspected endometriosis affects everyday life or symptoms continue or worsen despite treatment. Options can include painkillers, hormonal treatments and surgery, depending on the situation. Fertility plans belong in the discussion because treatment choices change when someone is trying to conceive.⁶

The “Bringing It to the Appointment” section of Period, Handled recommends recording what pain prevented you from doing, which treatments you tried and for how many cycles.

For a discussion about melatonin, bring separate notes for period pain, pain on other days, sleep and side effects. Agree on the symptom being targeted, the review date and the reasons to stop or seek advice. Keep the existing endometriosis treatment plan under review with the team rather than replacing it with an unmonitored supplement experiment.