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When administering a subcutaneous injection to an average-weight adult, which needle length and insertion angle is most appropriate?

  1. A1.5 inch needle at a 90-degree angle
  2. B5/8 inch needle at a 45-degree angle
  3. C1 inch needle at a 90-degree angle
  4. D1 inch needle at a 15-degree angle
Show answer & explanation

Correct answer: B. 5/8 inch needle at a 45-degree angle

Subcutaneous injections are given into the fatty tissue just below the skin, typically using a short 5/8 inch needle inserted at a 45-degree angle (or 90 degrees for a pinched fold in obese patients). Longer needles and steeper angles are used for intramuscular injections, which must reach deeper muscle tissue.

Why the other options are wrong

  • A. A 1.5 inch needle is too long and would likely enter muscle rather than subcutaneous tissue.
  • C. A 90-degree angle with a 1 inch needle is more consistent with an IM injection technique.
  • D. A 15-degree angle is used for intradermal injections, not subcutaneous.

Subcutaneous Injection Technique

Injections given into the fatty layer below the dermis, typically using a short needle at a 45-degree angle.

  • Needle length: 5/8 inch (sometimes 1/2 inch)
  • Angle: 45 degrees (90 degrees if pinching skin fold in obese patients)
  • Common sites: abdomen, upper arm, thigh

Memory trick: '15 for ID, 45 for SubQ, 90 for IM'

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