All praise is due to Allah the Lord of the worlds. I send salutations and peace to our Prophet Muhammad, his family and all his companions Wa ‘alaykum salaam wa rahmatullahi wa barakaatuhu To proceed: Injecting the sick person with medication through the veins does not break fast according to the majority of contemporary scholars, and that is because injecting medication in the veins is neither eating nor drinking, nor something with the qualities of eating and drinking. The principle is that fasting is valid until there is clear proof of its nullification, and there is nothing to indicate that. As to what you have mentioned that the procedure of injection requires injection of a small quantity of water; this does not also affect fasting, because it is in line with what had been mentioned previously that it is neither food nor drink nor something which has the qualities of food and drink, and the principle is that fasting is valid. This is from one angle. On other hand it can be said that the level of the water that is used is little, and does not break the fast. It is like the water that remains in the person who has made wuthoo‘, and it is known that the water which remains in the mouth of the person who has made wuthoo‘ does not break fast according to an opinion that was agreed upon by the scholars; and it is a small amount which is not required.
Dr. Khaalid al-Mosleh 19/10/1428 AH