Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.134B.
Section : Fasting, any type of injection.
Injections do not break the fast whether they are for feeding the person or just medicine. It does not matter if the injection was intravenous or underneath the skin. It also does not matter if what was injected reaches the stomach, as it does not reach the stomach through the customary manner (that food does).