NHA Certified Clinical Medical Assistant (CCMA)Clinical Patient CareHard
A medical assistant is preparing to administer an influenza vaccine to an adult patient via intramuscular (IM) injection. The MA should select a needle with which of the following gauges and lengths?
- A23 gauge, 5/8 inch
- B27 gauge, 0.5 inch
- C25 gauge, 1.5 inch
- D21 gauge, 1 inch
Show answer & explanationAnswer & explanation
Correct answer: D. 21 gauge, 1 inch
For an adult IM injection, a 21-23 gauge needle is typically used. The length of 1 to 1.5 inches is appropriate for the deltoid muscle in most adults to ensure the medication reaches the muscle layer. 21 gauge allows for easier fluid flow for vaccines.
Why the other options are wrong
- A. A 5/8 inch needle is typically too short for an IM injection in most adults, risking subcutaneous administration instead of intramuscular.
- B. A 27-gauge needle is generally too small for IM injections, and a 0.5-inch length is definitely too short for IM administration in an adult.
- C. A 25-gauge, 1.5-inch needle could be used, but 21 gauge is often preferred for IM, and 1.5 inches may be longer than necessary for the deltoid in all adults.
Adult IM Needle Selection (Deltoid)
Appropriate needle gauge and length for intramuscular injections into the deltoid muscle of an adult.
- Gauge: 21-23 G.
- Length: 1-1.5 inches.
- Ensures muscle penetration.
Memory trick: IM Needles: Gauge is inversely proportional to diameter, Length depends on site/patient.