Does evening primrose oil help with irregular periods during perimenopause?

Evening primrose oil may have some modest influence on menstrual symptoms during perimenopause, but the direct evidence for regularizing irregular cycles is limited. Its most plausible contribution is reducing the pain, cramping, and discomfort that often accompany unpredictable cycles, rather than restoring a regular monthly pattern. Here is what the biology suggests and where the honest gaps in the evidence lie.

Irregular periods during perimenopause happen because of erratic follicle development. The ovaries become less consistent in releasing mature eggs, which means progesterone production after ovulation is also irregular. Without consistent progesterone, the uterine lining builds and sheds unpredictably, leading to cycles that may be shorter, longer, heavier, lighter, or simply skipped. This is a normal feature of the hormonal transition, not a disorder, and it reflects the fundamental shift happening in the ovaries over months to years. No supplement fully reverses that underlying process, because the irregularity comes from ovarian aging rather than from a deficiency that can be corrected.

Evening primrose oil contains gamma-linolenic acid (GLA), an omega-6 fatty acid that the body converts into dihomo-gamma-linolenic acid (DGLA) and then into prostaglandin E1, which has anti-inflammatory properties. Prostaglandins play a direct role in menstruation. Pro-inflammatory prostaglandins, particularly prostaglandin F2-alpha, cause uterine contractions and contribute to cramping during menstruation. By shifting the prostaglandin balance toward the less inflammatory E1 type, GLA may reduce dysmenorrhea, the cramping and pain associated with menstruation. This could make periods that do come more manageable, even if it does not make them more predictable. Some practitioners also suggest GLA affects menstrual flow characteristics such as clotting and heaviness, though the evidence for this specific effect is largely anecdotal.

There is a small amount of research suggesting EPO may reduce premenstrual symptoms including cramping, breast tenderness, and cycle-related discomfort, which relates to perimenopausal menstrual changes. However, no controlled trials have specifically studied EPO for cycle regularity in perimenopausal women. The evidence is genuinely limited here. Chasteberry (vitex agnus-castus), for instance, has somewhat more direct research on menstrual cycle support than EPO does, though its evidence for perimenopause is also far from conclusive. Both should be discussed with a provider rather than used without guidance.

In EPO research for perimenopausal symptoms broadly, doses of 3,000 to 4,000 mg per day, divided with meals, have been used. Taking EPO with food helps reduce the most common side effects, which include nausea and loose stools. Some women start lower and increase gradually over two to three weeks. Talk to your healthcare provider about the right dose for your situation.

Evening primrose oil may interact with blood thinners and anticoagulants. It may also lower the seizure threshold, so discuss with your provider if you take any seizure medications. If you take blood thinners, antidepressants, or any prescription medications, check with your provider before adding this supplement.

If you have or have had a hormone-sensitive condition such as breast cancer, endometriosis, or uterine fibroids, discuss evening primrose oil with your healthcare provider before using it.

Expect to give EPO four to eight weeks before evaluating any effect, since menstrual patterns take at least a few cycles to assess. Keep in mind that during perimenopause, cycles naturally continue to shift regardless of supplementation, which makes it genuinely difficult to separate any EPO effect from the ongoing hormonal transition. This is one reason tracking your cycle carefully is so valuable during this time.

See your doctor if periods become extremely heavy, meaning soaking through more than one pad or tampon per hour for several consecutive hours. Also seek evaluation for bleeding after sex, bleeding between periods that is new or unusual, or going more than 90 days without a period when you have not reached menopause. These patterns can indicate fibroids, polyps, endometrial changes, or other conditions that need proper medical assessment. Heavy or irregular bleeding is one of the most common reasons perimenopausal women need clinical evaluation, and a supplement is not a substitute for that conversation.

The PeriPlan app (https://apps.apple.com/app/periplan/id6740066498) lets you log irregular periods daily so you can spot whether patterns shift over time and bring accurate cycle data to your healthcare provider appointments.

This content is for informational purposes only and does not replace medical advice. Always consult your healthcare provider about your specific situation.