Intramuscular Injections are a more evasive form of injection vs subcutaneous injections. Intramuscular Injections are meant to inject the compound directly into the muscle tissue, which typically requires a longer, larger gauge needles. The needles can range between 28 gauge and larger. However, Rejuvi Medical uses 1- inch, 23-25 gauge needles, which most mclients claim they cannot feel when administered into the glutes (the bum). While intramuscular needles may seem scary for some, the actual shot with such small gauge needles usually has almost no irritation or pain.