Intramuscular Injection Technique

Injection Angle

The standard angle for IM injections is 90 degrees perpendicular to the skin surface, as recommended by the Advisory Committee on Immunization Practices (ACIP) and the American Academy of Family Physicians 1, 2, 3, 4
This 90-degree angle is critical because deviating from the recommended route can reduce medication efficacy or increase local adverse reactions 4

Needle size: 7/8 to 1 inch length, 22-25 gauge, as recommended for infants 1, 2, 3, 5
Injection site: Anterolateral aspect of the thigh, which provides the largest muscle mass in infants 1, 5

Needle size: 7/8 to 1¼ inches length, 22-25 gauge, as recommended for toddlers and children 1, 2, 5, 6
Injection site: Deltoid muscle if adequate muscle mass is present; otherwise anterolateral thigh, as recommended by the American Academy of Family Physicians 1, 7
For toddlers using the thigh, the needle should typically be 1 inch long 1, 5

Needle size: 1 to 1½ inches length, 22-25 gauge, as recommended for adults 1, 2, 3, 5, 6
Injection site: Deltoid muscle (preferred) or anterolateral thigh, as recommended by the American Academy of Family Physicians 1, 7

Never use the buttock for IM injections due to the risk of sciatic nerve injury and decreased immunogenicity from inadvertent subcutaneous or deep fat tissue injection, as recommended by the Advisory Committee on Immunization Practices (ACIP) 1, 2, 3, 7, 8
The needle must be long enough to reach muscle mass and prevent medication from seeping into subcutaneous tissue, but not so long as to involve underlying nerves, blood vessels, or bone 1, 5, 6

Aspiration is not necessary: Although some practitioners advocate for aspiration before injection, no data support this as a required procedure, as stated by the Centers for Disease Control and Prevention (CDC) 1, 5, 6
When administering multiple IM injections in the same limb, separate injection sites by more than 1 inch to differentiate any local reactions, as recommended by the American Academy of Family Physicians 1, 5, 6

Using inadequate needle length for patient body size, which results in subcutaneous rather than intramuscular delivery and reduced medication efficacy, as warned by the Centers for Disease Control and Prevention (CDC) 1
Injecting into the buttock, which carries both safety risks (sciatic nerve injury) and efficacy concerns (decreased drug absorption), as warned by the American Academy of Family Physicians 1, 7, 8
Failing to individualize needle selection based on age, muscle mass, and injection volume, as a one-size-fits-all approach increases the risk of improper administration, as stated by the Advisory Committee on Immunization Practices (ACIP) 1, 5

The Centers for Disease Control and Prevention, as reported in MMWR Recommendations and Reports, recommends injecting volumes of 0.5-1 mL for routine deltoid vaccinations, with a maximum recommended volume of 1-2 mL for routine deltoid injections in adults 9
For larger volumes (>2 mL), the anterolateral thigh or ventrogluteal site should be used instead, as these sites have greater muscle mass, according to MMWR Recommendations and Reports 9
The American Academy of Pediatrics and other organizations likely support the use of a needle length of 1 to 1½ inches (25-38 mm) and a needle gauge of 22-25 gauge for deltoid injections, as suggested by MMWR Recommendations and Reports 9
When administering multiple injections, separate injection sites by >1 inch (2.5 cm) if using the same limb, and document the location of each injection in the medical record, as recommended by MMWR Recommendations and Reports 9