Does evening primrose oil help with hot flashes during perimenopause?

Evening primrose oil is one of the better-studied non-hormonal supplements for hot flashes during perimenopause, and the evidence, while modest, is real. Two randomized controlled trials have specifically tested it for vasomotor symptoms, showing meaningful reductions in hot flash severity and frequency. If you are looking for a non-prescription option, EPO has a stronger evidence base for hot flashes than for most other perimenopausal symptoms.

Hot flashes occur when declining estrogen disrupts the hypothalamus, the brain region that regulates body temperature. The thermoregulatory set point becomes narrower and more sensitive, so small changes in core temperature trigger a cascade of blood vessel dilation, sweating, and flushing that can last anywhere from a few seconds to several minutes. This process is driven in part by changes in norepinephrine signaling in the hypothalamus and by pro-inflammatory prostaglandins that alter vascular reactivity. The experience ranges from mild warmth to a drenching, disabling episode, and frequency varies widely between women.

Evening primrose oil contains gamma-linolenic acid (GLA), an omega-6 fatty acid that the body converts to dihomo-gamma-linolenic acid (DGLA) and then to prostaglandin E1, an anti-inflammatory compound. Prostaglandin E1 has vasodilatory and temperature-regulatory effects that appear to work differently from the inflammatory prostaglandins involved in triggering hot flashes. By competing with pro-inflammatory prostaglandins for the same enzymatic pathways, GLA may help reduce the severity and frequency of vasomotor episodes. GLA also modulates estrogen receptor sensitivity, which may help the body respond more smoothly to the fluctuating estrogen levels of perimenopause.

The key clinical evidence comes from two randomized trials. Chenoy and colleagues (1994) conducted a double-blind, placebo-controlled trial using 3 grams of EPO per day. They found that women taking EPO experienced fewer and less severe hot flashes compared to placebo, with a meaningful reduction in maximum daily hot flash episodes and fewer night-time episodes. Kazemi-Bajestani and colleagues (2014) similarly found reductions in both hot flash frequency and severity in perimenopausal women taking EPO compared to placebo. These are not large trials, and the effect sizes are modest rather than dramatic, but they provide genuine controlled evidence rather than just anecdote. This is more than most supplements for hot flashes can claim.

Studies have used doses of approximately 3,000 to 4,000 mg of EPO per day, typically divided across two or three meals. Taking EPO with food improves tolerability and may aid absorption since GLA is fat-soluble and absorbs better alongside dietary fat. The GLA content varies by brand, so check labels for actual GLA milligrams rather than just total EPO content when comparing products. Talk to your healthcare provider about the right dose for your situation.

EPO is not a replacement for hormone therapy, which has significantly stronger and more consistent evidence for vasomotor symptom relief. For women with moderate to severe hot flashes, or for those whose quality of life is significantly affected, a conversation with a healthcare provider about all available options including hormone therapy is important before settling on a supplement approach alone. EPO supplements do not replace prescribed treatments and are best positioned as part of a broader management strategy.

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.

Give EPO four to eight weeks before making a judgment. Hot flash patterns can vary week to week even without intervention, so a short trial may not give you a clear picture. Some women begin noticing reduced intensity within four to six weeks; others need closer to eight weeks at a consistent dose to see meaningful change.

See your doctor if hot flashes are severe, occurring more than seven times per day, significantly disrupting sleep, or accompanied by irregular heartbeat, unexplained weight changes, or other new symptoms, as thyroid dysfunction can closely mimic vasomotor symptoms.

The PeriPlan app (https://apps.apple.com/app/periplan/id6740066498) lets you log hot flashes daily so you can spot whether patterns shift over time and track whether EPO is producing a real change in frequency or severity.

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