Syrup: B-vitamins including Vitamin C are Water-soluble vitamins they are excreted in the urine and less likely to cause issues but taking very large doses can be potentially dangerous and may cause excessive thirst, skin conditions, blurry vision, abdominal cramps, nausea, vomiting, increased urination, diarrhea and too much b-vitamins in long term use can lead to nerve damage. Seek for immediate medical attention if the patient is experiencing these symptoms.