What needle gauge range and length would you use for an infant, an adult, and an obese adult?

• A. Infant: 23-25g 3/8 to 5/8 inch (Correct)
• B. Infant: 20-22g 1 inch; Adult: 25-27g 1/2 inch; Obese adult: shorter needle
• C. Infant: 18-20g 5/8 inch; Adult: 25-27g 1/2 inch; Obese: 1 inch
• D. Infant: 23-25g 1-2 inch; Adult: 20-22g 2-3 inch; Obese: shorter needle

Answer: (A)

Matching needle size to patient size and injection depth is essential. For an infant getting an intramuscular injection, you want a small-diameter needle that can reach the muscle without going too deep. A gauge in the 23–25 range with a length of about 3/8 to 5/8 inch fits this need, minimizing tissue trauma while still delivering the medicine into muscle.

The other options use needles that are either too thick or too long for an infant, which increases discomfort or risk of injury. For adults, IM injections are typically given with a gauge around 22–25 and a length around 1 inch, but for much of the exam material, the focus is that infants require the shorter, finer needle. Obese adults generally need a longer needle to reach muscle, not a shorter one, so that part of the alternatives is inconsistent with proper technique.

So the choice that aligns with standard practice for infants—small gauge and short length—best fits the question’s focus.