Interferon is injected subcutaneously (i.e., in the subcutaneous tissue layer between the skin and the muscle), rather than intramuscularly. One disadvantage of regular interferon is that it is metabolized very quickly, with a half-life in the body of only 4 hours after absorption. In turn, its side effects prevent it from being injected as frequently as antibacterial drugs. This affects the efficacy of interferon. In order to prolong the metabolism of interferon in the body, doctors have come up with the idea of replacing intramuscular injections with subcutaneous injections. Scientists have confirmed that the absorption and utilization of interferon is greater with subcutaneous injections than with intramuscular injections. Because the blood vessels in the muscle are rich, absorption is faster and metabolism is also faster; while the blood vessels under the skin are less, absorption is slower, metabolism is also slower, and interferon is more fully utilized. Therefore, the absorption rate and utilization rate of interferon subcutaneous injection are better than intramuscular injection. The sites for subcutaneous injection can be chosen: the subcutaneous tissues of the upper arm, abdomen, buttocks and outer thighs. I found a diagram from a foreign website and translated and modified it to make it clearer for everyone to see.