Subcutaneous injections deliver medication into the layer of fatty tissue, or subcutis, found just beneath the skin. This route of administration is frequently used because the subcutaneous layer contains fewer blood vessels than muscle tissue, allowing for a slower, more sustained absorption of the medication into the bloodstream. Many medications, such as insulin and certain blood thinners, are administered this way, often enabling individuals to safely self-administer treatment at home.
Preparing the Supplies and Medication
Before beginning, meticulous hand hygiene is necessary to reduce the risk of infection. Hands should be washed thoroughly with soap and warm water for at least 20 seconds before gathering the required materials. All items should be placed on a clean, dry surface, including the medication, the syringe or injector pen, alcohol wipes, gauze, and a puncture-resistant sharps disposal container.
The medication requires careful inspection before preparation. Check the expiration date on the vial or pen, and examine the liquid for any changes in color or clarity that might indicate contamination. If the medication is refrigerated, such as some types of insulin, allow it to warm to room temperature for about 30 minutes before injection, as cold medication can cause discomfort. If using a multi-dose vial, wipe the rubber stopper clean with a fresh alcohol swab and allow it to air dry completely before drawing the dose.
Selecting and Preparing the Injection Site
Selecting the correct anatomical location is important for the medication’s effectiveness and to minimize tissue damage. Appropriate sites for subcutaneous injections include:
- The fatty tissue over the abdomen, avoiding the two-inch area immediately surrounding the navel.
- The outer aspect of the upper arms.
- The front and outer areas of the thighs.
- The upper buttocks, particularly for certain long-acting medications.
Consistently rotating the injection site helps prevent a condition called lipohypertrophy, which is a buildup of fatty tissue and scar tissue under the skin. Repeated injections into the same area can lead to lumps that interfere with the reliable absorption of the medication. Individuals should choose a new spot for each injection that is at least one inch away from the previous site, systematically rotating through the available areas of the body.
The chosen site should be inspected for any existing bruises, scars, moles, or inflammation, which must be avoided. Injecting into compromised tissue can affect absorption and increase the risk of discomfort or infection. To prepare the skin, use a fresh alcohol wipe to clean the area with a circular motion, moving outward from the center. Allow the alcohol to dry fully before proceeding, as injecting through wet alcohol can cause stinging and may carry the antiseptic deeper into the tissue.
Step-by-Step Injection Technique
Once the site is ready and the syringe is prepared with the correct dose, the injection technique can begin. To ensure the medication reaches the subcutaneous layer and avoids the underlying muscle, gently create a fold of skin and hold it between the thumb and forefinger. This skin fold should be approximately one to two inches wide, especially for individuals with less fatty tissue or when using a longer needle.
The angle of needle insertion is determined by the amount of subcutaneous fat and the length of the needle. If a two-inch skin fold can be easily created, or if the needle is shorter (4mm to 5mm), insert the needle straight in at a 90-degree angle. If the individual is very thin, or if a longer needle is being used, insert the needle at a 45-degree angle to ensure the tip remains within the fatty layer and does not reach the muscle.
The needle should be inserted quickly in a smooth, dart-like motion to minimize pain. Once the needle is fully inserted, the skin fold can be released before the medication is pushed. The plunger should be pushed steadily and slowly to deliver the entire dose of the medication, which allows the tissue to accommodate the liquid comfortably.
After the plunger is fully depressed, the needle should remain in place for a short duration, usually counting to 5 or 10, before being withdrawn. This hold time ensures the entire dose is delivered and prevents the medication from leaking back out through the needle track. Remove the needle quickly and smoothly at the same angle it was inserted to avoid unnecessary tissue dragging or discomfort.
Post-Injection Safety and Disposal
Following the injection, a small drop of blood or minor bruising at the site may occur, which is normal. If bleeding is present, light pressure can be applied gently to the area with a piece of clean gauze. It is important not to rub or massage the injection site, as this action can irritate the tissue beneath the skin and may accelerate the absorption of the medication, potentially impacting its intended effect.
The most important step after the injection is the immediate and safe disposal of the used needle and syringe. Needles should never be recapped after use to prevent accidental needle-stick injuries. The entire used unit must be placed immediately into an approved sharps container—a specialized puncture-resistant, leak-proof container with a tight-fitting lid.
If an FDA-cleared sharps container is unavailable, a heavy-duty plastic container, such as a laundry detergent bottle, can be used as a temporary alternative; avoid glass or thin plastic containers. The container should be kept out of reach of children and pets, and it must never be placed in household trash or recycling bins. When the container is about three-quarters full, seal it and dispose of it according to local community guidelines, which often involve drop-off sites or special waste collection programs.