I say, and with Allah's success: If a fasting person takes an injection during the day of Ramadan, it does not invalidate their fast, whether the injection is subcutaneous, like an insulin injection, or intramuscular, or intravenous, or in any part of the outer body; because such an injection does not reach the stomach through the considered openings. As for the rectal injection, it breaks the fast because it is a considered opening. And Allah knows best.