When used in amounts available in food or supplements, bilberry is safe for consumption with no known side effects, but as of 2015, there are no studies to show the effects of bilberry, according to the National Center for Complimentary and Integrative Health. However, high doses of bilberry may cause toxic effects.
The bilberry is similar to a blueberry, and people commonly use the fruit to make jam or pie, as explained by the National Center for Complimentary and Integrative Health. People in Europe also use bilberry as a traditional medication, and they have done so for almost 1,000 years. The berry grows in Europe, North America and parts of Asia, and people traditionally use it to treat scurvy and diarrhea. In contemporary practice, people use bilberry to treat diarrhea, eye problems, menstrual cramps, varicose veins and venous insufficiency, which is a condition in which the veins cannot efficiently send blood into the heart from the legs.
People also use bilberry to treat other conditions, including diabetes, and to improve night vision, according to the National Center for Complimentary and Integrative Health. People either eat bilberry for these effects or take an extract of the fruit. People may also steep the leaves of the bilberry plant to make tea or form the leaves into an extract. Those who choose to take bilberry supplements should talk to a doctor about adding it to the diet.