Receiving injections, glucose and mannitol while fasting What is the ruling on receiving injections (painkillers, antibiotics, etc.) and on using glucose and mannitol while fasting? Answer Injections, glucose and mannitol (a diuretic used by patients suffering from ocular hypertension) do not invalidate fasting because they do not enter the body through an open orifice but through the skin. They are absorbed by the skin and there is no difference between this and injecting them into the body. And God Almighty knows best.