What is the maximum IM injection volume for the arm?

• A. 3 mL
• B. 5 mL
• C. 2 mL
• D. 1 mL

Answer: (C)

The question tests the maximum intramuscular injection volume that the deltoid (the upper arm) can safely receive. The deltoid is a relatively small muscle with limited capacity, and it sits close to bone, nerves, and subcutaneous tissue. To ensure the drug is deposited primarily into muscle tissue and to minimize pain, tissue distension, or accidental deposition into subcutaneous tissue, the volume is kept modest. About 2 mL is considered the upper limit for this site in adults, which is why 2 mL is the best choice. Larger volumes are better suited to bigger muscles like the gluteal sites (where up to roughly 5 mL can be tolerated). In clinical practice, many deltoid injections are 0.5–1 mL, with 2 mL as the practical ceiling.