Recommended Needle Size and Gauge for Intramuscular Injections
For intramuscular (IM) injections in adults, a 22-25 gauge needle with length of 1-1.5 inches is recommended, with specific adjustments based on patient size, injection site, and age. 1
Needle Selection by Age Group
Infants (< 12 months)
- 22-25 gauge, 7/8-1 inch needle for anterolateral thigh (preferred site) 1
- Subcutaneous injections: 23-25 gauge, 5/8 inch needle 1
Toddlers and Children (12 months-18 years)
- 22-25 gauge, 7/8-1¼ inch needle for deltoid or anterolateral thigh 1
- Deltoid can be used if muscle mass is adequate 1
Adults (≥19 years)
- Weight-based needle length recommendations:
- Adults <60 kg (130 lbs): 25 mm (1 inch) needle 1
- Adults 60-70 kg (130-152 lbs): 25 mm (1 inch) needle 1
- Men 70-118 kg (152-260 lbs): 25-38 mm (1-1½ inches) needle 1
- Women 70-90 kg (152-200 lbs): 25-38 mm (1-1½ inches) needle 1
- Men >118 kg (260 lbs): 38 mm (1½ inches) needle 1
- Women >90 kg (200 lbs): 38 mm (1½ inches) needle 1
Needle Selection by Injection Site
Deltoid Site
- Adults: 22-25 gauge, 1-1½ inch needle 1
- Consider arm circumference: use longer needle (>1 inch) when arm circumference exceeds 35 cm for men and 30 cm for women 2
Anterolateral Thigh
Ventrogluteal/Dorsogluteal Sites
- Adults: 22-23 gauge, 1½ inch needle 1, 3
- For obese patients: Consider needle longer than 1.5 inches, especially for women with BMI >24.9 kg/m² 3
- Note: Buttock should not be used for vaccine administration due to risk of sciatic nerve injury and decreased immunogenicity 1
Special Considerations for Obese Patients
- Subcutaneous tissue thickness increases with BMI, requiring longer needles to reach muscle 1, 3
- For women with BMI >24.9 kg/m², use needles longer than 1.5 inches for gluteal injections 3
- In extremely obese patients, subcutaneous tissue thickness can exceed 50 mm at gluteal sites 3
- Consider using deltoid site in obese patients when possible, as it has less subcutaneous tissue 4, 3
Injection Technique Tips
- Insert needle at 90-degree angle to ensure proper muscle penetration 1
- For patients at risk of IM injection (children, thin adults), use a lifted skinfold technique 1
- Needle should be long enough to reach muscle mass but not so long as to involve nerves, blood vessels, or bone 1
- The ventrogluteal site is farther from neurovascular structures (11.82 ± 14 mm to superior gluteal nerve) compared to dorsogluteal site (5.67 ± 9 mm) 5
Common Pitfalls to Avoid
- Using too short a needle in obese patients, resulting in subcutaneous rather than intramuscular deposition 4, 3
- Using the dorsogluteal site for vaccinations (risk of sciatic nerve injury) 1
- Using the same needle length for all patients regardless of body habitus 1, 3
- Failing to consider site-specific differences in subcutaneous tissue thickness 1, 3
Remember that proper needle selection is crucial for ensuring medications reach the intended muscle tissue, which affects both efficacy and safety of the administered medication 1.