Injection Routes

Injection Routes

– Intramuscular
– Subcutaneous
– Intradermal

It is strongly recommended that healthcare workers maintain and follow their facility’s guidelines for aseptic medication preparation and use safety-engineered devices to reduce the risk of needlestick injury after use and to minimize exposure to blood/body fluid.

Intramuscular (IM):

An injection into the muscle tissue (typically less than 3 mL). Large volumes require larger muscles (e.g., vastus lateralis), while smaller volumes (up to 1 mL) can be administered in smaller muscles (e.g., deltoid).

Muscle sites have a good blood supply, which helps the medication to be absorbed more rapidly than by the subcutaneous route. The intramuscular route is also used if a medication is likely to irritate subcutaneous tissue. Some of the drugs given by this route are antibiotics, vitamins, vaccines and fertility drugs.

Intramuscular injections require identification of anatomical markers to assure proper placement.
Important note: infants <18 months old should not receive an IM injection of >0.5 mL.

Vastus lateralis muscle:
Tolerates volumes up to 5 mL in adults. Maximum volume for ages between 3-13 years is 1.5 mL, 1 ½ – 3 years is 1 mL. <1 ½ years, 0.5 mL. Maximum needle length for children is 1 inch.

Ventrogluteal site:
Maximum volume is 3 mL in adults, 2mL for ages between 6-13 years, 1.5 mL for between 3-6 years, and 1 mL for ages between 1 ½ – 3 years. May be the safest and least painful IM injection site.

Dorsogluteal site:
Not recommended unless required by drug manufacturer; do not use in children less than 3 years old. Maximum volume is 3 mL in adults, 2mL for ages between 6-13 years, and 1.5 mL for between 3-6 years. Risks: Proximal to the sciatic nerve, superior gluteal artery, and the possibility of injecting medication into the thick layer of subcutaneous tissue over the muscle.

Deltoid muscle:
used for volumes of ≤1mL in adults and 0.5 mL in children between 18 Risk: Proximal to the radial nerve and the brachial artery.

Subcutaneous (SubQ):

An injection into the fatty layer which lies beneath the dermis. This route is used for small volume injections (≤1 mL) and when the medication is not likely to irritate or damage the subcutaneous tissue. The blood supply to the subcutaneous tissue is less than in muscle tissue; therefore, the absorption rate is generally slower than with IM injections. This is desirable for some medications (e.g., insulin).

Some patients (e.g., malnourished or elderly) may not have enough subcutaneous tissue for a SubQ injection. Check with prescriber to determine if an alternative route is acceptable.

Skin/Subcutaneous Thickness: Appropriate needle length and injection technique is dependent on the patient’s skin and subcutaneous fat thickness. Intramuscular injections can be avoided with the use of shorter needles.

Injection sites may have different absorption rates. With animal and human insulins, the abdomen has been shown to have the most rapid absorption, the upper arms intermediate, and the thigh and buttocks the slowest absorption. Rotating insulin injections within a site (at least 1” from previous injection) and using needles only once may avoid the development of lipodystrophy while maintaining a more predictable absorption.

Intradermal (ID):

An injection into the dermis. Only a very small volume of fluid is given (0.1 mL or less). This route is used to test a patient’s sensitivity to allergens or for tuberculin testing.* It is also used for administering local anesthetics. * Due to the risk of anaphylactic reaction, emergency medication and equipment should be available.

If used, allow the alcohol from an alcohol swab to dry completely prior to injection.

Following administration, do not apply pressure or massage injection site.

Inject with the needle bevel up.

If a wheal, or bleb, does not appear during administration, the medication is being delivered into the subcutaneous tissue.