Peace be upon you. It is obligatory for the fasting person to avoid injections of nourishing or strengthening substances altogether, as well as intravenous injections and all types of serum. However, there is no objection to using non-nourishing injections administered intramuscularly, such as antibiotics, painkillers, and anesthetic injections.
Source: [Answers to Inquiries, S767](https://www.leader.ir/ar/book/14/%D8%A7%D8%AC%D9%88%D8%A8%D8%A9-%D8%A7%D9%84%D8%A5%D8%B3%D8%AA%D9%81%D8%AA%D8%A7%D8%A1%D8%A7%D8%AA?sn=5422).
According to Grand Ayatollah Sistani, introducing medication or similar substances through an injection into the muscle or vein is permissible.
Source: [Minhaj al-Salihin, Vol. 1, Issue 985](https://www.sistani.com/arabic/book/23720/4698/).
May you be successful in all good.