Certified Medical Assistant (CMA AAMA)PharmacologyMedium
A medical assistant is preparing to administer 0.5 mL of a vaccine intramuscularly to an adult patient. Which of the following needle lengths is most appropriate for a deltoid injection?
- A1 1/2 inches
- B1/2 inch
- C1 inch
- D5/8 inch
Show answer & explanationAnswer & explanation
Correct answer: C. 1 inch
For intramuscular injections into the deltoid muscle of an average-sized adult, a 1-inch needle is typically recommended to ensure the medication reaches the muscle tissue and not just the subcutaneous layer.
Why the other options are wrong
- A. 1 1/2 inches is often used for IM injections in larger muscles like the ventrogluteal or vastus lateralis, or for obese patients.
- B. 1/2 inch is too short for an intramuscular injection in an adult deltoid; it's typically used for intradermal.
- D. 5/8 inch is generally used for subcutaneous injections or very thin adults/children for IM.
Deltoid IM Needle Length
For adult deltoid intramuscular injections, a 1-inch needle length is generally appropriate to ensure muscle penetration.
- Needle length depends on patient size and injection site.
- Must reach the muscle layer for IM injections.
- Too short, and medication may go into subcutaneous tissue.
Memory trick: Deltoid IM: 'One' inch is the one to pick.