There are four intramuscular sites where an injection may go, and the choice depends on the patient's preference, unless the doctor specifically advises on a location, according to About.com. These sites have little fatty tissue and are large and markable.
The acceptable muscles for an intramuscular injection include the deltoid, vastus lateralis, ventrogluteal and dorsogluteal muscles, explains About.com. The deltoid muscle is below the shoulder on the upper arm. To find the site, place the palm of the hand on the shoulder, and then spread the fingers upside down in a V-shape. The injection goes into the center of the V.
The vastus lateralis muscle is in the thigh, and to find it, divide the top of the thigh into three parts from the top to bottom, states About.com. The injection should go into the middle section. The ventrogluteal muscle is in the hip, and to find the injection location, another person should place a hand on the thigh of the person needing the injection, with the thumb pointing to the groin and the fingers pointing to the head. Find the bony area at the edge of the ring and pinkie fingers, spread them into a V-shape, and then give the injection between them.
The dorsogluteal muscle is the large muscle of the backside, claims About.com. To place an injection, look at one buttock, and divide it into four quadrants. Place the injection into the upper outer quadrant near the hip.