What size needle is recommended for an intramuscular (IM) deltoid injection?

Recommended Needle Size for IM Deltoid Injection

For adults, a 22-25 gauge, 1-1½ inch needle is recommended for deltoid intramuscular injections. 1, 2

Needle Size Recommendations by Age Group

• Adults (>18 years): 22-25 gauge, 1-1½ inch needle for deltoid IM injections 1, 2
• Children (12 months-18 years): 22-25 gauge, 7/8-1¼ inch needle when using the deltoid muscle (if muscle mass is adequate) 1, 2
• Infants (<12 months): 22-25 gauge, 7/8-1 inch needle primarily for anterolateral thigh (deltoid can be used if necessary) 1

Factors Affecting Needle Length Selection

• Gender differences: Women have significantly thicker deltoid fat pads (11.7 mm vs 8.3 mm in men), requiring careful consideration of needle length 3
• Body weight considerations:
  • For women <60 kg: 5/8-inch (16 mm) needle may be sufficient 3
  • For women 60-90 kg: 1-inch (25 mm) needle recommended 3
  • For women >90 kg: 1.5-inch (38 mm) needle needed to ensure intramuscular administration 3
  • For men across weight ranges (59-118 kg): 1-inch (25 mm) needle is generally sufficient 3

Injection Technique

• Insert the needle at a 90-degree angle to ensure proper muscle penetration 2
• The needle should be long enough to reach the muscle mass but not so long as to involve underlying nerves, blood vessels, or bone 1
• For all intramuscular injections, ensure the needle can penetrate through subcutaneous tissue and reach the muscle to prevent vaccine from seeping into subcutaneous tissue 1

Optimal Injection Site

• The recommended site is approximately 4 cm distal to the posterolateral corner of the acromion 4, 5
• This site maximizes successful intramuscular administration while minimizing risk of overpenetration and avoiding the axillary nerve 4
• Never inject in the upper half of the deltoid muscle to avoid injury to underlying neurovascular structures 5

Common Pitfalls to Avoid

• Using too short a needle: In obese patients, standard 25 mm needles may be insufficient to reach muscle tissue, particularly in women with BMI >35 2, 6, 7
• Using the same needle length for all patients: Consider patient's body habitus, sex, and BMI when selecting needle length 2, 3
• Improper injection site: Injecting too high in the deltoid increases risk of injury to the axillary nerve and posterior circumflex humeral artery 4, 5
• Buttock injections: Avoid using the buttock for vaccine administration due to risk of sciatic nerve injury and decreased immunogenicity 1, 2

Special Considerations for Obese Patients

• In patients with obesity, skin-to-deltoid-muscle distance increases significantly 7
• For obese females with BMI >35, a 32 mm (1.25 inch) or longer needle may be required 6
• Consider arm circumference and BMI when selecting needle length, as both factors influence skin-to-muscle distance 7