Hypersensitivity. atrophic gastritis, kidney or liver disease, Leber hereditary optic neuropathy, low amount of K in the blood, nervous system disorder, operation to remove stomach. Taking prescription, non-prescription, herbal prep or dietary supplement. Alcoholism. Infection, weakened eye nerve, build-up of waste in the blood, any kind of anemia or low blood levels of Fe or folic acid. Pregnancy, planning to become pregnant & breastfeeding.