Review note: AI-assisted draft independently checked against the cited sources by a separate AI reviewer. Not clinician-reviewed. Use with your course materials, supervised clinical training and current local policies.
For an intramuscular (IM) injection, connect the patient's age and muscle development with the medication, dose volume, and approved administration instructions. A site name alone cannot establish that an injection is appropriate.
Anatomy connection: See all four IM sites on the 3D muscle model.
Know the landmarks
| Site | Landmark summary | Key distinction |
|---|---|---|
| Ventrogluteal | Greater trochanter, anterior superior iliac spine, and iliac crest | Lateral hip; different from the buttock site |
| Deltoid | Central muscle below the acromion and above the axillary fold | CDC's preferred site for adult IM vaccines |
| Vastus lateralis | Middle third of the anterolateral thigh | Preferred for infant IM vaccination |
| Dorsogluteal | Upper outer buttock | Close to the sciatic nerve and major vessels; not a routine vaccine site |
For ventrogluteal landmarking, place the palm over the greater trochanter, point the thumb toward the umbilicus and index finger toward the anterior superior iliac spine, and spread the middle finger toward the iliac crest. The target lies within that V. Hand placement must accommodate the patient's anatomy. This region is relatively free of major neurovascular structures; that does not make it universally the safest choice for every injection. See the Australian Immunisation Handbook's landmark illustrations.
See the ventrogluteal site in 3D.
For the deltoid, expose and palpate the shoulder landmarks. CDC describes the adult vaccine target as approximately 2 inches below the acromion, above the axillary fold, in the thick central muscle. Distance alone does not replace landmarking. CDC adult IM guide.
For the vastus lateralis, identify the thigh between the greater trochanter and lateral knee, then use its outer middle third. For U.S. vaccine practice, CDC recommends this site for infants and prefers it for toddlers; a toddler's deltoid is an option when muscle mass is adequate. CDC vaccine administration guidance.
See the vastus lateralis site in 3D.
The dorsogluteal site is not preferred because of nearby nerves and vessels. Some medication protocols permit it, so “always wrong” is an unreliable exam shortcut. Vaccine site recommendations are distinct from medication protocols. Royal Children's Hospital (RCH) IM guideline.
See the dorsogluteal site and the sciatic nerve in 3D.
Volume: verify the patient and protocol
There is no single maximum for every adult or every child. Consider muscle development, medication characteristics, product labeling, and local policy. RCH, for example, recommends 1 mL for the deltoid but permits up to 2 mL, and distinguishes neonatal, child, and adult thigh volumes. These are institutional limits, not a universal NCLEX table. Do not transfer an adult capacity to an infant or assume a 1 mL deltoid limit applies to every patient. RCH guideline.
Adult deltoid vaccine needles
CDC uses 22–25 gauge needles. Its adult chart gives the following lengths:
| Adult weight category | Needle length |
|---|---|
| Less than 60 kg, either sex | 1 inch; see the exception below |
| 60–70 kg, either sex | 1 inch |
| Women over 70 through 90 kg; men over 70 through 118 kg | 1–1½ inches |
| Women over 90 kg; men over 118 kg | 1½ inches |
Some experts allow ⅝ inch for adults of either sex under 60 kg, only with skin stretched flat, no bunching of subcutaneous tissue, and a 90-degree insertion. Select a needle that actually reaches muscle. These vaccine recommendations do not establish needle choices for every IM medication. CDC adult IM guide.
Technique and practice reasoning
IM injections enter at 90 degrees. CDC does not recommend aspiration before vaccines at recommended sites. For other medications, follow the product and institutional procedure. CDC guidance.
Z-track displaces skin and subcutaneous tissue to help reduce medication leakage; use it when indicated by the medication procedure. RCH guideline.
- A 6-month-old needs an IM vaccine: identify the vastus lateralis and use age-appropriate vaccine guidance.
- An adult needs 2.5 mL of an IM medication: check the permitted sites and volume policy before selecting a sufficiently developed muscle. Volume alone cannot determine the answer.
- A nurse chooses the dorsogluteal site: evaluate the medication instructions, policy, and nerve-injury risk; do not rely on an absolute test-taking rule.
Open the IM sites view, inspect the landmarks, and use Practice to test recall.
AI-assisted educational content for exam preparation, independently checked against the linked guidance. This is not clinician review or a substitute for supervised skills instruction and medication-specific procedures.