Administer Injections

Injections are most commonly administered IM (intramuscular) or SC (subcutaneously)

Subcutaneous (SC) injections:

Route of administration for small volumes (0.5–1.0mL) of water-soluble medication into the loose connective tissue beneath the dermis. Absorption is slow, but usually complete in patients without circulatory compromise. Onset of action is delayed (up to 30–45 minutes).


  • Circulatory shock
  • Reduced local tissue perfusion
  • Very thin patients (may have inadequate adipose tissue for subcutaneous injection)
  • Bleeding diathesis

Anatomical sites

  • Central abdomen, below costal margins
  • Posterolateral aspect of upper arms
  • Anterior thigh
  • Scapular region of back.


  • Local tissue irritation, inflammation, erythema or pain.
  • Sterile abscess (collection of medication within the skin and appears as a hard painful lump).

Intramuscular (IM) injections

The IM route has certain advantages compared with SC administration, which include:

  • Faster rate of absorption (from 5 to 15 minutes) related to the greater vascularity of muscle.
  • Viscous solutions and substances irritant to subcutaneous tissues may be administered safely.
  • Larger volumes up to 3 – 5 mL can be given.


  • Known allergy
  • Circulatory shock
  • Reduced local tissue perfusion due to peripheral vascular disease
  • Bleeding disorder
  • Muscle atrophy.

Anatomical sites

Upper outer buttock (ventrogluteal)

  • This is a safe site for all patients and is the preferred site for adults and children over 7 months of age.
  • Locate the injection site by placing the heel of your hand over the greater trochanter of the hip, with the thumb directed towards the patient ’ s groin and fingers towards the patient’s head.
  • Place your index finger over the anterior superior iliac spine and extend the middle finger back over the iliac crest towards the buttock. This delineates a triangular area, the centre of which is the injection site.
  • Slight flexion of the hips and knee in the recumbent patient will relax the muscles.

Upper outer thigh (vastus lateralis)

  • Commonly used for IM injections in adults as it is thick, usually well-developed and easily accessible, even through clothing in an emergency such as for adrenaline in anaphylaxis.
  • Middle third of the muscle is the best site for administration and is located over the anterolateral aspect of the mid thigh.


  • Direct injection into blood vessel (always pull back on plunger to reduce this risk).
  • Sciatic nerve injury with incorrect approach. (Note: dorsogluteal approach is no longer used).
  • Brachial artery or radial nerve injury with deltoid injection.

CCC 700 6

Critical Care


BA MA (Oxon) MBChB (Edin) FACEM FFSEM. Emergency physician, Sir Charles Gairdner Hospital.  Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |

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