NHA Certified Clinical Medical Assistant (CCMA)Clinical Patient CareMedium
A medical assistant is preparing to administer an influenza vaccine via subcutaneous injection. Which of the following needle sizes is most appropriate for a subcutaneous injection in an adult?
- A18 gauge, 1 inch
- B27 gauge, 1/4 inch
- C25 gauge, 5/8 inch
- D21 gauge, 1.5 inches
Show answer & explanationAnswer & explanation
Correct answer: C. 25 gauge, 5/8 inch
Subcutaneous injections are administered into the fatty tissue just under the skin. A 25-gauge, 5/8-inch needle is a common and appropriate choice for adults, as it is thin enough for comfort and long enough to reach the subcutaneous tissue without penetrating muscle. Option D is too short for most adults, and A and B are too long/large for subcutaneous injections.
Why the other options are wrong
- A. An 18-gauge, 1-inch needle is too large in gauge and length for a subcutaneous injection; it's typically used for drawing viscous medications or for IM injections.
- B. A 27-gauge, 1/4-inch needle might be too short for many adults to reliably reach the subcutaneous tissue, though it's used for some specific applications like intradermal or very thin patients.
- D. A 21-gauge, 1.5-inch needle is typically used for intramuscular injections, not subcutaneous.
Subcutaneous Injection Needle Selection
Choosing the correct needle gauge and length for administering medication into the subcutaneous tissue layer.
- Gauge: 23-27 G (25 G common).
- Length: 1/2 to 5/8 inch (5/8 inch common).
- Administered at a 45- or 90-degree angle (depending on fat fold).
- Common sites: outer upper arm, abdomen, anterior thigh.
Memory trick: IM's Longer, SubQ's Shorter, ID's Shortest