Injection Sites and Techniques
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Direct answer
Injections are given by three common parenteral routes — intradermal, subcutaneous and intramuscular — distinguished by depth, needle angle and safe volume. Intradermal injections enter the dermis at 5–15 degrees (0.1 mL, Mantoux test), subcutaneous injections the fatty tissue at 45 degrees (up to about 1 mL), and intramuscular injections the muscle at 90 degrees (1–3 mL depending on the site). Correct site selection and landmarking prevent nerve injury, abscess and poor absorption.
What you must remember
- Intradermal: inner forearm, bevel up, 5–15 degrees, 0.1 mL; a small bleb should form, and the Mantoux test is read at 48–72 hours.
- Subcutaneous sites: abdomen (avoiding 5 cm around the umbilicus), outer upper arm and anterior thigh; rotate insulin sites to prevent lipohypertrophy.
- Intramuscular sites: deltoid (2–3 finger widths below the acromion, up to about 1 mL), vastus lateralis (middle third of the front-outer thigh, the preferred infant site), ventrogluteal (the safest gluteal site in older children and adults) and rectus femoris.
- Avoid the dorsogluteal site where possible — the sciatic nerve and gluteal vessels lie in its path; never inject into scarred, inflamed or oedematous tissue.
- Ventrogluteal landmark: palm over the greater trochanter, index finger on the anterior superior iliac spine, middle finger spread toward the iliac crest; inject into the centre of the triangle.
- Z-track for irritating drugs: pull skin and tissue sideways, inject, wait about 10 seconds, then release, sealing the drug within muscle.
- Typical needles: 21–23 gauge intramuscular, 25–27 gauge subcutaneous, fine tuberculin for intradermal; aspirate before intramuscular non-vaccine drugs (not for vaccines).
Common confusion
Students mix up the angles and the infant site. The sequence — 5–15, 45, 90 degrees for intradermal, subcutaneous and intramuscular — must be automatic. The vastus lateralis, not the deltoid or gluteal muscles, is the infant's routine site because the deltoid is small and the gluteal region risks sciatic injury. Ventrogluteal and dorsogluteal are also swapped: the ventrogluteal (side-lying, over the hip) is the safe modern choice, while the traditional dorsogluteal buttock site endangers the sciatic nerve.
Exam-focused takeaway
Expect landmark and angle questions: which site for a Mantoux test (inner forearm, intradermal), which muscle for a two-month-old's vaccine (vastus lateralis), which gluteal site is safest (ventrogluteal) and where not to give insulin (near the umbilicus, into lipohypertrophied areas). Know the Z-track steps and maximum volumes by site. Numerical one-liners on angles and gauges are routine, and procedure questions test the order — verify order, prepare site, landmark, inject, withdraw, document.
Frequently asked questions
At what angle is each injection given?
Intradermal 5–15 degrees bevel up, subcutaneous 45 degrees (90 with a short needle in a pinched fold), intramuscular 90 degrees.
Which is the preferred intramuscular site in infants?
The vastus lateralis — middle third of the anterolateral thigh — free of major nerves and vessels and well developed before walking age.
Why is the Z-track technique used?
It displaces the skin so the track seals on withdrawal, preventing leakage of irritating or staining drugs such as iron into subcutaneous tissue.
What volume can each site take?
About 0.1 mL intradermally, up to 1 mL subcutaneously, about 1 mL in the deltoid and 2–3 mL in a large muscle such as the ventrogluteal.
Where is the Mantoux test given and read?
Into the inner forearm intradermally, read at 48–72 hours by measuring induration, not redness, across the transverse diameter.