Evening primrose oil is pressed from the seeds of the evening primrose plant and contains omega-6 fats, including gamma-linolenic acid (GLA). As a supplement it is promoted for eczema, PMS, breast pain, menopause symptoms and rheumatoid arthritis.
Also known as: EPO, Oenothera biennis, GLA, gamma-linolenic acid.
There is no intake value or upper limit, and NCCIH gives no standard amount.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling.
What studies show: NCCIH says there is not enough evidence to support evening primrose oil for any health condition. Taken by mouth it has not been shown to help eczema, it is probably no better than placebo for breast pain, results for starting labor are inconsistent, and evidence is insufficient for rheumatoid arthritis, PMS and menopause. A 2013 Cochrane review of 27 studies concluded that evening primrose oil and borage oil are not effective treatments for eczema.
Safety: NCCIH says it is probably safe for most adults; the most common side effects are stomach pain, nausea and diarrhea. The Cochrane review notes a report that it may increase bleeding in people taking warfarin, and a case report raising concern about long-term use beyond a year. NCCIH says it may be safe in pregnancy and breastfeeding, but the evidence is not conclusive.
We could not find a single published half-life or time to peak for evening primrose oil that applies to a supplement dose, so we do not list one.
How Dose Track handles peptides · Reconstitution calculator · Half-life calculator