You can take water-soluble vitamins such as B and C with water during a fasting period. Vitamin C is usually pretty easy on an empty stomach, but B-complex vitamins can make you feel nauseous when it is consumed without food. If that happens to you, just take these vitamins when you break your fast. Fat-soluble vitamins such as A, D, E, K, should be taken with a meal. Supplements may be used during fasting periods, although some may be better absorbed with food. Supplements that contain calories or sugar are more likely to break your fast.
You must take your medicine as prescribed by your doctor.