Intramuscular Injection Sites: Nursing Study Guide

The four main intramuscular injection sites are the deltoid, ventrogluteal, vastus lateralis, and dorsogluteal muscles, and each one is found using bony landmarks rather than by eye. Choosing the right site, needle, and technique for the patient’s age and size helps the medicine reach the muscle and lowers the risk of nerve and tissue injury.

What is an intramuscular injection?

An intramuscular (IM) injection places medicine deep inside a large muscle. Muscles have a rich blood supply, so the drug reaches the circulation quickly and skips first-pass metabolism in the liver.

Common IM medicines include vaccines, immunoglobulins, some hormones, and antibiotics such as benzathine penicillin. IM injections are also chosen when a patient cannot take oral medicine or has trouble sticking to a treatment plan.

Intramuscular injection sites and landmarks

Learn each site as a pair: the landmark that finds it and the structure you are trying to avoid. The landmarks below are from StatPearls and the CDC.

Site	How to find it	Usually used for	Main risk to avoid
Deltoid (upper arm)	2.5 to 5 cm below the acromion process	Adults, adolescents, and children aged 3 to 10 years; toddlers if muscle mass is adequate	Radial nerve injury; shoulder injury after vaccination (bursitis, adhesive capsulitis, or tendinopathy)
Ventrogluteal (side of hip)	Heel of the opposite hand on the greater trochanter, index finger on the anterior superior iliac spine, and middle finger spread below the iliac crest; inject in the centre of the triangle formed	Adults	Fewer nerve injuries than the dorsogluteal site, but landmarks must still be exact
Vastus lateralis (anterolateral thigh)	Middle third of a line from the greater trochanter to the lateral femoral condyle of the knee	Infants and toddlers (preferred); alternative site in older children and adults	Femoral nerve injury has been reported
Dorsogluteal (buttock)	Upper outer quadrant of the buttock, 5 to 7.5 cm below the iliac crest	Now avoided where a safer site is available	Sciatic nerve and superior gluteal nerve injury

Which IM site to use by age

CDC vaccine guidance gives a clear age ladder that is also popular in exams. StatPearls lists the same pattern: vastus lateralis for infants, vastus lateralis or deltoid for children, and ventrogluteal or deltoid for adults.

• Infants (under 12 months): anterolateral thigh. A 1-inch needle is enough for most infants.
• Toddlers (12 months to 2 years): anterolateral thigh is preferred, with a needle of at least 1 inch. The deltoid can be used if the muscle mass is adequate.
• Children (3 to 10 years): deltoid is preferred (5/8 to 1 inch needle), with the thigh as an alternative (1 to 1.25 inch).
• Adolescents (11 to 18 years): deltoid is preferred, with the thigh as an alternative (1 to 1.5 inch).
• Adults (19 years and older): deltoid for vaccines, with needle length chosen by weight (Table 2).

IM needle length and gauge for adults

For IM vaccines, the CDC uses a 22- to 25-gauge needle at a 90-degree angle. The needle must be long enough to reach muscle but not so long that it hits nerves, blood vessels, or bone.

Adult weight	Deltoid needle length
Under 60 kg (130 lb)	5/8 inch, only if injected at 90 degrees without bunching the tissue
60 to 70 kg (130 to 152 lb)	1 inch
Women 70 to 90 kg; men 70 to 118 kg	1 to 1.5 inch
Women over 90 kg; men over 118 kg	1.5 inch

Tissue depth is not the same at every site. A 2023 meta-analysis of ultrasound studies found that subcutaneous fat over the ventrogluteal site averaged about 20 mm and was thicker in women than in men, which is one reason needle length should be matched to the patient.

How to give an IM injection: key steps

These steps follow the sequence described in StatPearls. Your facility’s procedure always comes first.

1. Check the order against the medication administration record and confirm the right patient, drug, dose, site, and time.
2. Explain the procedure, get consent, and choose a suitable site.
3. Perform hand hygiene, put on gloves, and clean the skin with 70% isopropyl alcohol for 30 seconds, then let it dry.
4. When drawing up, use a filter needle and change it before injecting. Do not draw up an air bubble.
5. Use the Z-track technique and insert the needle at 90 degrees with a quick, dart-like motion.
6. Aspiration: StatPearls advises aspirating for 5 to 10 seconds for dorsogluteal injections, while the CDC says aspiration is not needed for vaccines at the recommended sites. Follow local policy.
7. Inject slowly, at about 10 seconds per mL, then wait 10 seconds before withdrawing the needle smoothly.
8. Discard the needle straight into a sharps container (StatPearls describes the one-handed scoop method if recapping is needed), then assess the site for early complications.

Contraindications to IM injection

• Infection, cellulitis, or dermatitis at the injection site
• Known allergy to the drug
• Thrombocytopenia or other bleeding and clotting problems
• Hypovolaemic shock, because poor muscle blood flow can delay absorption
• Myopathy or muscle wasting
• Acute myocardial infarction, because the release of muscle enzymes can complicate management

Complications of IM injections

StatPearls lists both early and late problems. The most important ones for nurses to recognise are:

• Persistent pain, abscess, or skin sloughing at the site
• Nerve injury: sciatic (gluteal sites), femoral (vastus lateralis), superior gluteal (dorsogluteal), and radial (deltoid)
• Shoulder injury after deltoid vaccination
• Muscle fibrosis and contracture
• Nicolau syndrome, vascular injury, and infection

The sciatic nerve is the nerve most often injured, and nearly 90% of patients with this injury have foot drop straight away. Most of these injuries are preventable with correct site choice and landmarks.

Nursing assessment

• Allergies and the reason the IM route is needed
• Platelet count, clotting problems, and anticoagulant use
• Muscle mass, body weight, and the skin at each possible site
• Previous injection sites, so injections are spread out

Nursing considerations

• Give each injection at a different site. CDC advises spacing two injections in the same limb at least 1 inch apart and recording each site.
• To reduce pain, StatPearls lists the ventrogluteal site over the dorsogluteal site, the Z-track technique, a slow injection rate, and an internally rotated foot for gluteal injections.
• Document the drug, dose, site, time, and patient response, and check the site again later.
• Teach the patient to report increasing pain, swelling, numbness, or weakness.

Exam tips

• Baby = thigh: the vastus lateralis is the preferred site for infants.
• V for ventrogluteal, V for very safe: it has a better safety profile than the dorsogluteal site.
• Buttock plus foot drop = sciatic nerve injury.
• Trap: CDC says hepatitis B vaccine given anywhere other than the deltoid or anterolateral thigh in adults, and rabies vaccine given in the buttock, should not be counted.
• Angle: IM injections go in at 90 degrees.

Frequently asked questions

Which IM injection site is the safest?

No site is risk-free, but StatPearls notes that the ventrogluteal site has a better safety profile than the dorsogluteal site, which causes most injection-related sciatic nerve injuries. For vaccines, the CDC recommends the deltoid for adults and the anterolateral thigh for infants. Always locate the site using the correct bony landmarks.

Why is the thigh used for infant injections?

CDC guidance recommends the anterolateral thigh (vastus lateralis) for most infants under 12 months, usually with a 1-inch needle. The deltoid is only considered later, in toddlers, once the arm has enough muscle mass. StatPearls lists the same pattern, so in exams the answer for an infant is the thigh.

Do you need to aspirate before an IM injection?

For vaccines, the CDC says aspiration is not needed because there are no large blood vessels at the recommended sites. StatPearls still advises aspirating for 5 to 10 seconds when the dorsogluteal site is used. Practice differs, so follow your facility’s policy and the drug’s instructions.

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• All nursing study guides

Sources

• Intramuscular Injection. StatPearls, NCBI Bookshelf (last updated 13 September 2026).
• Vaccine Administration. General Best Practice Guidelines for Immunization, Centers for Disease Control and Prevention (2024).
• Gluteal muscle and subcutaneous tissue thicknesses in adults: a systematic review and meta-analysis. Gulnar E, et al. Journal of Research in Nursing (2023).

This article is for education only and does not replace advice from your own doctor, nurse, or other qualified health professional. Always follow your facility’s policies and reference ranges.