Evening Primrose Oil

Evening primrose oil is often bought on reputation. These are the questions our naturopaths ask in store, so you choose the right thing.

A good fit if

• Dry skin is why you're reaching for it, because that's where the evidence is best
• Night sweats bother you more than hot flushes, which is the difference the menopause trials found
• You want GLA specifically, because ordinary food gives you almost none
• You'd rather have the honest version of a famous supplement than the marketing one
• You can take it with food, which helps prevent stomach upset

Check with us first if

• You take warfarin or another blood thinner. Evening primrose oil has been reported to increase bleeding in people on warfarin.
• You have surgery, a tooth extraction or a procedure coming up. A 2022 trial found it lowered platelet activity, and the effect lasted beyond the last capsule.
• You take antiretroviral medicine for HIV. A systematic review found evening primrose oil significantly raised antiretroviral medicine levels, which needs monitoring.
• You take medicine for inflammatory bowel disease. It's one of the herbs reviewed for possible interactions in that group.
• You're breastfeeding. The evidence isn't clear either way, so it's worth a conversation rather than a label instruction.
• You plan to take it for more than a year. The Cochrane review says the short-term studies can't speak to long-term use, and one case report raised concerns beyond twelve months.
• You've been told to avoid it because of epilepsy. That warning was formally re-examined in 2007 and found to be unfounded, but many references still include it, so check rather than assume either way.
• You take prescription medicines. Check with your doctor, pharmacist or our naturopaths before you start.

• Evening primrose oil, standard 1,000 mg capsule. Best known for: The standard here, and the form almost every Australian product uses. Absorption: The fats do reach you. Trials that measured fats in the blood and skin saw DGLA rise while people took it. Typical use: One or two capsules a day, which is the dose the menopause trials used.
• Hi-strength or concentrated evening primrose oil. Best known for: More GLA per capsule, so you need fewer capsules for the same amount. Absorption: There's no separate absorption trial; it's absorbed the same way as the standard capsule. Typical use: Matching a trial dose of 2,000 mg a day with fewer capsules.
• Evening primrose oil with fish oil. Best known for: Adds the omega-3s EPA and DHA alongside the omega-6 GLA, which is the whole reason the blend exists. Absorption: There's no direct comparison with plain evening primrose oil. The pairing covers both families of fats rather than improving absorption. Typical use: People who would otherwise buy two bottles. It isn't a stronger evening primrose oil.
• Evening primrose with starflower (borage seed oil). Best known for: Starflower is borage seed oil, and it's the richer source of GLA of the two. Absorption: There's no direct absorption trial against evening primrose oil. Typical use: Allowed only as the fixed seed oil of Borago officinalis, so check the label says seed oil.
• Blackcurrant seed oil. Best known for: The third GLA seed oil, which also contains stearidonic acid. Absorption: Not measured against the other two. Typical use: Usually sold inside a blend rather than on its own. It's allowed in its own right as Ribes nigrum.
• Topical evening primrose oil and gamma-linoleic acid. Best known for: The difference is in the regulations, not the effect, and it's the labelling trap in this family. Absorption: Not applicable. This one goes on the skin. Typical use: Gamma-linoleic acid is limited to medicines applied to the skin. Gamma-linolenic acid, one letter different, isn't.

Reference values. There isn't one. Evening primrose oil isn't an essential nutrient, so the NHMRC sets no recommended intake for it. The NHMRC does publish an Adequate Intake for linoleic acid, but it isn't in the reference data we used, so we haven't quoted a number rather than guess.

Typical supplemental range. Australian capsules are almost always 1,000 mg of oil, taken one to three times a day. The trials that found anything used one or two of them. The night sweats result came from 1,000 mg twice a day for eight weeks. Some older research used several times that, at doses no Australian label recommends, so don't copy a study dose from a headline.

Upper level. None has been set. Australia's permitted ingredients list (Schedule 1) has no maximum daily dose for evening primrose oil, Oenothera biennis, Oenothera stricta or gamma-linolenic acid, and the NHMRC sets no upper limit either. Treat the directions on the label as your limit.

Worth knowing. The common side effects are stomach-related, so take the capsules with food. Long-term use is the genuine unknown here, and the Cochrane authors say plainly that the short-term studies can't answer that. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Evening primrose seed oil: 70 to 74 per cent linoleic acid, 8 to 10 per cent GLA
• Borage (starflower) seed oil: the richest of the common seed-oil GLA sources
• Blackcurrant seed oil: GLA plus stearidonic acid, usually sold inside a blend
• Evening primrose root: boiled and eaten like potatoes historically. A food use, not a GLA source
• Evening primrose leaves and shoots: young leaves cooked as greens, shoots eaten raw. Also historical
• Everyday food: GLA is close to absent, and no reliable per-serve figures exist, so none are quoted

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• Warfarin and other blood thinners. Increased bleeding has been reported, so check with your prescriber.
• Antiplatelet medicines and planned surgery. Platelet activity fell in a 2022 trial and stayed down after people stopped taking it.
• Antiretroviral treatment. A systematic review found it significantly raised antiretroviral drug levels, so monitoring is needed.
• Pregnancy. Clinical review advice is to avoid it; sources conflict, and we follow the cautious one.
• Breastfeeding. The evidence isn't conclusive, so see a practitioner rather than assume it's fine.
• Children. There's no established dose, and less is known about safety.
• Medicines for inflammatory bowel disease. It's named among herbs reviewed for possible interactions.
• Taking it for more than a year. Long-term safety hasn't been studied, and a single case report raised concerns.
• Upset stomach and headache. These are the common side effects, and they're mild and short-lived. Take it with food.
• Epilepsy. The old warning against use was rebutted in 2007 but still appears in references, so check with your doctor.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before you start.