Ampules: Small glass containers of liquid medication ranging from 1 mL to 10 mL sizes.

Bleb: A small, raised circle that appears after administration of an intradermal medication indicating correct placement into the dermis.

Deltoid: Commonly used for intramuscular vaccinations in adults because it has a triangular shape and is easy to locate and access. The injection site is in the middle of the deltoid muscle, about 1 to 2 inches below the acromion process.

Gauge: Refers to the diameter of a needle. Gauges can vary from very small diameter (25 to 29 gauge) to large diameter (18 to 22 gauge).

Intradermal injection: Medication administered in the dermis just below the epidermis.

Intramuscular injection: Medication administered into a muscle.

Intravenous injection: Medication administered directly into the bloodstream.

Subcutaneous injection: Medication administered into the subcutaneous tissue just under the dermis.

Vastus lateralis: A muscle located on the anterior lateral aspect of the thigh and extends from one hand’s breadth above the knee to one hand’s breadth below the greater trochanter. It is commonly used for immunizations in infants and toddlers because the muscle is thick and well-developed.

Ventrogluteal: The safest intramuscular injection site for adults and children because it provides the greatest thickness of gluteal muscles, is free from penetrating nerves and blood vessels, and has a thin layer of fat.

Z-track method: A method for administering intramuscular injections that prevents the medication from leaking into the subcutaneous tissue, allows the medication to stay in the muscles, and minimizes irritation.