A 22 to 25 gauge needle is used for an intramuscular (IM) injection, states Scott & White Healthcare. When administering IM injections, needle length should also be considered as it should be long enough to reach the specific muscle. Intramuscular injections are used to administer vaccines and different drugs, notes Healthline.
Intramuscular injections are administered to different muscle groups, such as the buttocks, upper arm region, hip and thigh. The needle has to penetrate through skin and different tissues to reach these deep muscles. For this reason, the needle has to be a specific length that is dependent on factors such as patient size and age, states Healthline. An adult who weighs between 130 and 152 pounds may require a needle that is 1 inch in length. The needle length for a newborn, by contrast, is 5/8 inch, notes Scott & White Healthcare.