Supplements for Endometriosis: What the Research Shows

No supplement is a proven treatment for endometriosis, and the evidence for each one is small. A few supplements, mainly vitamins C and E, vitamin D and melatonin, lowered endometriosis pain in small trials, but other trials found no difference from a placebo.

So a supplement can be something to talk about with your doctor, next to the treatment you already have. It is not a replacement for it. This guide shows what the studies found for each supplement, the doses they used, how strong the evidence is, and who should be careful.

Quick answer: how strong is the evidence?

When the trials are put together, antioxidant supplements seem to ease endometriosis period pain. But the groups were small and the results varied a lot, so the review authors were only moderately confident about period pain and had very little confidence in the results for pelvic pain and pain during sex.

Most of the trials had 30 to 60 women and ran for 6 to 24 weeks. That is too few women to be sure, and too short to show long-term safety.

Vitamins C and E

In two trials, women with endometriosis who took vitamin C and vitamin E together had less pelvic pain and less pain during sex than women on a placebo. In one of them, pelvic pain went down by 43% and period pain by 37%. In the other, period pain did not improve more than with a placebo.

How strong: The trials are small and do not prove cause and effect. Only about 150 women took part in the three trials of this combination.

Doses in the trials: 1,000 mg of vitamin C a day with 800 to 1,200 IU of vitamin E a day, for 8 weeks. These are trial doses, not a proven dose.

Who should be careful: 540 mg (800 IU) or less a day of vitamin E supplements is unlikely to cause harm. One trial used more than that, and not enough is known about what high daily doses of vitamin E do. Talk to a doctor before you take a dose above that amount.

Vitamin D

The vitamin D trials do not agree. In one trial, vitamin D lowered pelvic pain more than a placebo. In another, pain went down by the same amount with vitamin D as with a placebo, and a third trial after surgery found no difference. The trial that lowered pelvic pain, which gave 50,000 IU every 2 weeks, also eased period pain, and another trial at 50,000 IU a week did not.

How strong: The evidence is suggestive rather than definitive. The trials used very different doses, so no dose for endometriosis pain is clear.

Doses in the trials: Most trials gave 50,000 IU once a week or once every 2 weeks for 12 weeks. One gave 2,000 IU a day for 6 months.

Who should be careful: The high trial doses are far above the safe daily limit for adults who take vitamin D on their own. Do not take more than 100 micrograms (4,000 IU) of vitamin D a day, unless your doctor tells you to. Too much over a long time can make calcium build up in the blood, which can weaken the bones and damage the kidneys and the heart. Some medical conditions mean you cannot safely take as much, so check with your doctor if you are not sure.

Melatonin

In two small trials, melatonin eased endometriosis period pain more than a placebo. One of them also found less pelvic pain. The trials gave 10 mg or 5 mg a day for 8 weeks, with 40 women in each trial.

How strong: These are small trials, and only two of them. They are a reason for more research, not proof that melatonin works for endometriosis.

Who should be careful: Short-term use appears safe for most adults, but the long-term effects are not clear. Side effects include headache, dizziness, nausea and sleepiness. Talk to a doctor first if you take a blood thinner, have epilepsy, or are pregnant or breastfeeding. Melatonin products may not contain the amount on the label, and in some countries melatonin is a prescription medicine.

N-acetylcysteine (NAC)

In one study of 120 women, NAC lowered period pain, pain during sex and pelvic pain over 3 months, and fewer women needed anti-inflammatory painkillers. The women took 600 mg tablets, 3 tablets a day, on 3 days in a row each week. The authors saw no side effects.

How strong: This study had no comparison group. All the women took NAC, so the study cannot show if the pain went down because of NAC or for other reasons. The authors say larger studies are necessary to confirm their results.

Omega-3 (fish oil)

Two small trials gave omega-3 fish oil to people with endometriosis. Neither found less period pain than with a placebo, and the one that checked pain during sex found no difference there either.

Omega-3 fats from food, such as oily fish, are part of an anti-inflammatory diet for endometriosis. That guide covers what to eat. For bloating, see the endo belly diet.

Resveratrol

In one trial with 44 women, 40 mg of resveratrol a day for 6 weeks did not lower period pain more than a placebo.

What about magnesium and ginger?

Magnesium and ginger have small trials for ordinary period cramps, not for endometriosis. Our guide to magnesium and ginger for period cramps shows what those trials found.

Safety: tell your doctor before you start

Tell your doctor or pharmacist about every supplement you take, and say how much you take. This is important if you take hormone treatment, painkillers, a blood thinner or any other regular medicine, if you plan surgery, or if you are trying to get pregnant.

• High doses are not the same as safe doses. Some trials used doses of vitamin D and vitamin E that are above the safe daily amount for people who take them without a doctor's care.
• Supplements are not checked like medicines. In the US, supplements have less strict control than medicines, and some products do not contain what the label says.
• A supplement does not replace treatment. Hormone treatment, pain medicine and surgery have much stronger evidence. Our endometriosis treatment options guide compares them.

What is not known

• Long-term safety and effect. The trials ran for 8 weeks to 6 months, so they do not show what happens after years of use.
• The right dose. The trials used different doses and schedules, so no dose is proven for endometriosis.
• Who benefits. The groups were small, so the studies cannot show which people with endometriosis, if any, benefit most.
• Fertility. The evidence that vitamins improve fertility in endometriosis is limited and inconclusive.

Track what you try

If you and your doctor agree to try a supplement, keep a record before you start and while you take it. Write down what you take, how much, and from which day. In Endolog, log your pain severity, where it hurts, your bleeding and other symptoms each day, and note the supplement in the food diary. After two or three cycles, you can show your doctor a PDF report and see together if your pain changed.

When to see a doctor

See a doctor if your pain stops you from work, school or sleep, if painkillers do not help, or if your pain gets worse over time. Get urgent help if you have sudden, severe pain in your belly or pelvis, pain with a fever, or you faint, and more so if you could be pregnant.

Endometriosis pain is real, and you deserve treatment that works for you.

FAQ: supplements for endometriosis

What is the best supplement for endometriosis?

No supplement is proven to treat endometriosis. Vitamins C and E have the most consistent results, but only in a few small trials. Talk to your doctor before you start any supplement.

Does vitamin D help endometriosis pain?

The trials disagree. One trial found less pelvic pain with high-dose vitamin D, but others found no difference from a placebo. Do not take more than 4,000 IU a day unless your doctor tells you to.

Does NAC help endometriosis?

One study found less pain after 3 months of NAC, but it had no comparison group, so it cannot prove that NAC caused the change.

Can supplements replace hormone treatment for endometriosis?

No. The evidence for supplements is small, and they are not a replacement for the treatments with stronger evidence. If you want to try one, use it next to your treatment and tell your doctor.

Does fish oil help endometriosis?

Probably not. Two small trials found no difference from a placebo for period pain.