In adults, where are injections most commonly given?

• A. Gluteus maximus
• B. Deltoid
• C. Vastus lateralis
• D. Quadriceps

Answer: (B)

In adults, injections are most commonly given into the deltoid muscle of the upper arm. This site is easily accessible, allows quick absorption of vaccines or small-volume medicines (typically about 0.5 mL to 1 mL), and is straightforward to locate by feeling the point a few centimeters below the shoulder bone.

Other sites exist but are used less often for routine injections in adults. The gluteus maximus has a long history as an IM site but can be harder to target accurately and carries a higher risk of hitting a nerve or causing variable absorption, so it’s less favored now. The vastus lateralis is commonly used for infants and small children because their gluteal region isn’t ideal, and in adults it isn’t the standard choice for routine IM injections. The term quadriceps isn’t a typical site for IM injections in adults compared with the deltoid.