Quick answer

NIH says high doses of vitamin E supplements might increase the risk of bleeding and of serious bleeding in the brain, which is why the adult upper limit is 1,000 mg a day. A meta-analysis of nine trials found 22% more hemorrhagic strokes. Vitamin E from food has not been found to cause harm.^1,2,3

Key facts

NIH says high doses of vitamin E supplements might increase the risk of bleeding by reducing the blood's ability to clot.^1,2
A 2010 meta-analysis of nine trials with 118,765 people found hemorrhagic stroke was 22% more likely with vitamin E, about one extra case per 1,250 people, with no change in total stroke.³
A 2021 meta-analysis of 18 studies put the hemorrhagic stroke estimate at 1.17 (0.98 to 1.39), not statistically significant, and called for more trials.⁴
With anticoagulant or antiplatelet medicines, NIH says the amounts of vitamin E needed for clinically significant effects are unknown but probably exceed 400 IU a day.¹
Vitamin E in food has not been found to cause harm and does not need to be limited.^1,2

What NIH says about vitamin E and bleeding

NIH's consumer sheet says that in supplement form, high doses of vitamin E might increase the risk of bleeding, by reducing the blood's ability to form clots after a cut or injury, and of serious bleeding in the brain, known as hemorrhagic stroke. That is the reason for the upper limit.²

High doses of vitamin E supplements might increase the risk of bleeding, by reducing the blood's ability to clot after a cut or injury, and of serious bleeding in the brain (hemorrhagic stroke).^1,2

Two trials found more hemorrhagic strokes in people taking vitamin E: Finnish male smokers taking 50 mg a day for about 6 years, and US male doctors taking 400 IU (180 mg) of synthetic vitamin E every other day for 8 years, most of whom also took aspirin.¹

NIH adds that high doses cause hemorrhage and interrupt blood coagulation in animals, and that test-tube data suggest high doses inhibit platelet aggregation. Because most physicians in one of the trials also took aspirin, NIH says the finding could point to a tendency to cause bleeding.¹

What do meta-analyses of trials show?

A 2010 meta-analysis pooled nine randomized trials with 118,765 people. Vitamin E had no effect on total stroke, with a relative risk of 0.98. It raised the risk of hemorrhagic stroke by 22%, with a relative risk of 1.22 and a range of 1.00 to 1.48, which the authors put at about one additional case for every 1,250 people taking vitamin E. The two types of stroke moved in opposite directions, and the authors cautioned against indiscriminate widespread use.³

A 2021 meta-analysis of 18 studies with 148,016 people found no significant difference in total stroke, and a hemorrhagic stroke estimate of 1.17 with a range of 0.98 to 1.39, which did not reach statistical significance. Its authors said the trials were not large enough to settle the question and that more were needed.⁴

Read together, the reviews agree on the direction of the hemorrhagic estimate and disagree on whether it is statistically certain.^3,4

Does vitamin E thin the blood or cause clots?

NIH describes it as slowing clotting at large doses, not as causing clots. It says vitamin E can inhibit platelet aggregation and work against vitamin K-dependent clotting factors, so taking large doses with an anticoagulant or antiplatelet medicine such as warfarin can increase the risk of bleeding, especially with low vitamin K intake.¹

Ask your pharmacist or doctor first

Vitamin E can slow the clumping of platelets and work against the clotting factors that depend on vitamin K. Taking large doses with an anticoagulant or antiplatelet medicine, such as warfarin, can therefore increase the risk of bleeding, especially when vitamin K intake is low. NIH says the amount needed to cause a clinically significant effect is not known.^1,2

Expected from how the two work, not shown in studies

People who bruise or bleed easily while taking vitamin E, or who are about to have surgery, are among those who should ask their doctor about it.¹

Does vitamin E cause constipation, diarrhea, acne or weight gain?

The sources checked do not report constipation, diarrhea, acne or weight gain as effects of vitamin E taken by mouth, which is not a finding either way. NIH names bleeding, a higher rate of prostate cancer in one large trial, and heart failure hospitalizations in another, as concerns at high doses.¹

Who should ask a doctor about vitamin E and bleeding

Anyone who takes a blood thinner such as warfarin, or an antiplatelet medicine, and also takes vitamin E.¹
Anyone with a bleeding disorder, a history of stroke or a surgery or dental procedure ahead.¹
Anyone considering a supplement of 400 IU a day or more.^1,2

Questions people ask

Does vitamin E cause bleeding?

NIH says high doses of vitamin E supplements might increase the risk of bleeding and of hemorrhagic stroke. Ask your doctor, especially if you take a blood thinner.^1,2

Does vitamin E cause blood clots?

NIH describes the opposite effect at large doses: slower clotting, with possible bleeding. It does not report vitamin E causing clots in the sources checked.^1,2

Does vitamin E cause bruising?

NIH describes a bleeding risk at high doses, which can include bleeding after a cut or injury. Bruising is not named separately in the sources checked. Ask your doctor.²

Does vitamin E cause constipation, diarrhea, acne or weight gain?

The sources checked do not address these effects, which is not a finding either way. Ask your doctor or pharmacist if a symptom follows a new supplement.¹

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.