Studies have found that some compounds of grape seed extract may be effective in relieving symptoms of chronic venous insufficiency (when veins have problems sending blood from the legs back to the heart) and reducing edema (swelling) after an injury or surgery. It may require at least 1 month to see the benefits of grape seed extract when used for this purpose.
There is limited evidence to support the efficacy of grape seed extract in treating other conditions.
Grape seed extract is generally well-tolerated when taken by mouth. Side effects that have been reported include abdominal pain, diarrhea, dry mouth, upset stomach, headache, join pain, and nausea. In rare cases, people may develop signs of a serious allergic reaction, such as swelling of the face or throat, hives, or difficulty breathing.
Grape seed extract may cause changes in the way the body processes drugs, and could potentially alter the effects of many drugs. It is also known to interact with the following:
- anticoagulants (e.g., apixaban, warfarin)
- cyclosporine
- midazolam
- vitamin C
Contact your health care provider before taking grape seed extract if you are pregnant or breast-feeding.
Grape seed extract may increase your risk of bleeding. Ask your health care provider before taking it if you have a bleeding disorder. Stop taking grape seed extract at least 2 weeks before surgery.
Grape seed extract should not be taken for more than 3 months or if your symptoms worsen.
Before taking any new medications, including natural health products, speak to your physician, pharmacist, or other health care provider. Tell your health care provider about any natural health products you may be taking.