Maximum Volume for Intramuscular Injection
The maximum recommended volume for intramuscular (IM) injection is 0.5 mL in the deltoid muscle for adults and children ≥3 years, 0.25 mL for infants 6-35 months, and up to 50 μL in the caudal thigh muscles of rodents. 1, 2
Volume Limits by Anatomical Site and Age
Deltoid Muscle (Humans)
- Adults and children ≥3 years (36 months): Maximum 0.5 mL 2, 1
- Infants and toddlers 6-35 months: 0.25 mL (age-dependent based on vaccine formulation) 2, 1
- Critical safety note: A 0.5 mL prefilled syringe should never be split into two 0.25 mL doses due to sterility concerns and compliance issues with vaccine excise taxes 2, 1
Anterolateral Thigh (Vastus Lateralis)
- Preferred site for infants and young children for IM injections 2, 1
- Can accommodate larger volumes than the deltoid and provides more rapid absorption for certain medications 1
- The thigh is recommended when volumes exceed 0.5 mL or when the deltoid muscle mass is inadequate 1
Rodent Models (Mice)
- Maximum 50 μL in caudal thigh muscles to ensure intramuscular retention 2, 3
- At 100 μL, mild to moderate leakage into extramuscular tissues occurs 3
- At 200 μL, moderate to severe extramuscular leakage is observed, compromising pharmacokinetics 3
- Use the finest needle possible (27G or smaller) in quadriceps or caudal thigh muscle 2
Physiological Rationale for Volume Restrictions
Larger volumes risk inadequate muscle penetration, subcutaneous deposition, local pain, reduced absorption, and increased adverse reactions. 1
- Concentrated solutions in smaller volumes cause less muscle damage than larger volumes of diluted solutions 4
- Injection speed is not a critical factor in muscle damage, but volume and concentration are 4
- Muscle distention from excessive volume is painful and can affect locomotion, particularly in animal models 2
Site Selection Algorithm
For adults and older children:
- Use deltoid muscle with maximum 0.5 mL volume 2, 1
- Needle length >1 inch may be needed to penetrate muscle tissue adequately 1
- For children with adequate deltoid mass, use 7/8 to 1.25 inch needles 1
For infants and young children:
- Use anterolateral thigh as preferred site 2, 1
- Maximum 0.25-0.5 mL depending on age and vaccine formulation 2
- Avoid deltoid in this age group due to insufficient muscle mass 2
For volumes exceeding standard limits:
- Consider alternative sites such as the anterolateral thigh 1
- Never exceed recommended volumes in a single injection site 1
- Multiple injection sites may be required for larger total volumes 1
Critical Safety Considerations
- Epinephrine for anaphylaxis: 0.01 mg/kg of 1:1000 concentration (maximum 0.5 mg in adults, 0.3 mg in children) administered intramuscularly into the anterolateral thigh 2
- The vastus lateralis (anterolateral thigh) allows optimal absorption for emergency medications 2
- Avoid intramuscular injections in areas with lipohypertrophy, scars, or bony prominences 2