The major side effect of taking bilberry is a drop in blood sugar for certain patients, such as those taking medication for diabetes and who undergo surgery. Individuals should stop taking bilberry at least two weeks prior to having a scheduled surgical procedure, according to WebMD.
Bilberry is an alternative medical treatment available in different forms, such as in dried ripe berries, extract or leaf. Evidence supports bilberry as a possibly effective treatment for several abnormal conditions, such as circulation problems and retinal issues associated with high blood pressure and diabetes. Evidence, however, is contradictory to the claim that bilberry is an effective treatment for night vision problems, according to WebMD.
Insufficient evidence is available to determine if bilberry is effective in the treatment of dysmenorrhea, eye strain, glaucoma, irritable bowel syndrome, metabolic syndrome and weight loss. Effectiveness of treating other illnesses, such as chest pain, chronic fatigue syndrome, varicose veins, urinary tract issues, cataracts, hardening of the arteries, diabetes, arthritis, gout, skin problems and hemorrhoids, are under study, although the majority of claims do not have sufficient evidence to support them, says WebMD. Bilberry interactions, such as the interference with anticoagulants and antiplatelet drugs, slow blood clotting, possibly increasing the risk of bruising and bleeding; however, there is not enough evidence to support the seriousness of the risk.