Subcutaneous injection

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3D animation of a subcutaneous injection

A subcutaneous injection is administered as a bolus into the subcutis, the layer of skin directly below the dermis and epidermis, collectively referred to as the cutis. Subcutaneous injections are highly effective in administering medications such as insulin, morphine, diacetylmorphine and goserelin. Subcutaneous administration may be abbreviated as SC, SQ, sub-cu, sub-Q, SubQ, or subcut. Subcut is the preferred abbreviation to reduce the risk of misunderstanding and potential errors.[1]

Subcutaneous tissue has few blood vessels and so drugs injected here are for slow, sustained rates of absorption. It is slower than intramuscular injections but still faster than intradermal injections.

Medical uses[edit]

An insulin pump with a subcutaneous injection site

A subcutaneous injection is administered into the fatty tissue of the subcutaneous tissue, located below the dermis and epidermis.[2] They are commonly used to administer medications, especially those which cannot be administered by mouth as they would not be absorbed from the gastrointestinal tract. A subcutaneous injection is absorbed slower than a substance injected intravenously or in a muscle, but faster than a medication administered by mouth.[3]:721

Medications[edit]

Medications commonly administered via subcutaneous injection include insulin, monoclonal antibodies, and heparin.

Recreational drug use[edit]

Subcutaneous (as opposed to intravenous) injection of recreational drugs is referred to as "skin popping".


Technique[edit]

Subcutaneous injections are performed by cleaning the area to be injected followed by an injection, usually at an angle to the skin when using a syringe and needle, or at a 90-degree angle (perpendicular) if using an injector pen. The appropriate injection angle is based on the length of needle used, and the depth of the subcutaneous fat in the skin of the specific person. A 90-degree angle is always used for medications such as heparin. If administered at an angle, the skin and underlying tissue may be pinched upwards prior to injection. The injection is administered slowly, lasting about 10 seconds per milliliter of fluid injected, and the needle may be left in place for 10 seconds following injection to ensure the medicine is fully injected.[3]:724

Equipment[edit]

The gauge of the needle used can range from 25 gauge to 27 gauge, while the length can vary between ​12-inch to ​58-inch for injections using a syringe and needle.[3]:722 For subcutaneous injections delivered using devices such as injector pens, the needle used may be as thin as 34 gauge (commonly 30-32 gauge), and as short as 3.5mm (commonly 3.5mm to 5mm).[4] Subcutaneous injections can also be delivered via a pump system which uses a cannula inserted under the skin. The specific needle size/length, as well as appropriateness of a device such as a pen or pump, is based on the characteristics of a person's skin layers.[3]:722–724

Locations[edit]

Subcutaneous injection sites

Commonly used injection sites include:[3]:723

  • The outer area of the upper arm.
  • The abdomen, avoiding a 2-inch circle around the navel.
  • The front of the thigh, between 4 inches from the top of the thigh and 4 inches above the knee.
  • The upper back.
  • The upper area of the buttock, just behind the hip bone.

The choice of specific injection site is based on the medication being administered, with heparin almost always being administered in the abdomen, as well as preference. Injections administered frequently or repeatedly should be administered in a different location each time, either within the same general site or a different site, but at least one inch away from recent injections.[3]:724

See also[edit]

References[edit]

  1. ^ "ISMP's List of Error-Prone Abbreviations, Symbols,and Dose Designations" (PDF). www.ismp.org. 2013. Retrieved 13 May 2013.
  2. ^ "subcutaneous injection" at Dorland's Medical Dictionary
  3. ^ a b c d e f Taylor C (2011). Fundamentals of nursing : the art and science of nursing care (7th ed.). Philadelphia: Wolters Kluwer Health and Lippincott Williams & Wilkins. ISBN 978-0781793834.
  4. ^ Leonardi, Luca; Viganò, Mara; Nicolucci, Antonio (28 August 2019). "Penetration force and cannula sliding profiles of different pen needles: the PICASSO study". Medical Devices: Evidence and Research. 12: 311–317. doi:10.2147/MDER.S218983. PMC 6717876. PMID 31695523.