Where it is
Over the shoulder joint, from the clavicle, acromion and spine of the scapula to the deltoid tuberosity of the humerus.
What it does
Abducts the arm (raises it to the side); its front part flexes and its back part extends the arm.
Clinical relevance
- The deltoid injection site is 2–3 finger widths below the acromion process, in the center of the muscle.
- Injecting too low or too far back risks the radial and axillary nerves.
Nursing focus
- Use the deltoid for small volumes, typically 0.5–1 mL, such as vaccines.
- Expose the whole shoulder to see the landmarks; do not inject through rolled-up sleeves.