An intramuscular (IM) injection delivers medication directly into a muscle. Muscles have a rich blood supply, allowing faster absorption into the bloodstream. IM injections commonly administer treatments like antibiotics, vaccines, and hormone medications, or for pain relief and vitamin deficiencies. This route is useful when oral medications might lose potency in the digestive system or cause irritation if given intravenously.
Preparing for an Intramuscular Injection
Before administering an intramuscular injection, gather all necessary supplies. You will need the prescribed medication, a sterile syringe, an appropriately sized needle (typically 22-25 gauge and 1 to 1.5 inches long, varying by patient size and medication viscosity), alcohol swabs, gauze, and a sharps container. Gloves are also recommended for hygiene and to reduce contamination.
Wash hands thoroughly with soap and water to prepare medication from a vial. Inspect the vial for discoloration, cloudiness, or particles; verify medication, dose, and expiration date. Remove the protective cap and clean the rubber stopper with an alcohol swab, wiping in an outward circular motion for 10 seconds and allowing it to air dry.
To draw medication, attach the needle to the syringe. Pull back the plunger to draw air equal to the medication volume. Insert the needle through the center of the rubber stopper into the vial, then depress the plunger to inject air. This prevents a vacuum, making withdrawal easier. Invert the vial, ensuring the needle tip remains submerged, and slowly pull back the plunger to draw the precise dose.
After drawing medication, check the syringe for air bubbles by holding it needle-up and gently tapping the barrel. If bubbles are present, gently push the plunger to expel them back into the vial, then re-adjust to the correct volume. Remove the needle from the vial without touching it, and if instructed, replace the drawing-up needle with a new, sterile injection needle.
Select the correct injection site. Common options include the deltoid muscle (upper arm), vastus lateralis muscle (thigh), and ventrogluteal muscle (hip). The site should be free from pain, infection, bruising, or scars. Clean the skin area thoroughly with an alcohol swab and allow it to dry before injection.
Deltoid Muscle
The deltoid, in the upper arm, is about 1 to 2 inches below the acromion process. It is often used for smaller volumes, typically 2 mL or less.
Vastus Lateralis Muscle
The vastus lateralis, in the middle third of the thigh, is frequently chosen for infants and toddlers due to its well-developed muscle mass. It can also be used for self-administration.
Ventrogluteal Muscle
The ventrogluteal site, involving the gluteus medius and minimus muscles, is generally considered safest for adults and children. This is due to its substantial muscle thickness and distance from major nerves and blood vessels, accommodating larger volumes up to 3 mL.
Administering the Injection
Re-verify medication and dose. Position the individual comfortably, ensuring the injection site is fully exposed and relaxed. For instance, if using the deltoid, the arm should be relaxed at the side; for the vastus lateralis, the person can lie flat with the knee slightly bent or sit.
To stabilize the skin at the injection site, stretch the skin flat or use the Z-track method. This involves pulling the skin laterally away from the injection site before insertion. This technique helps seal medication within the muscle, minimizing irritation or leakage into the subcutaneous tissue. Hold the syringe like a dart with your dominant hand, using your non-dominant hand to stabilize the skin around the injection area.
With a swift, smooth, dart-like motion, insert the needle into the muscle at a 90-degree angle to the skin. The needle must be long enough to penetrate subcutaneous tissue and reach deep into the muscle, typically 1 to 1.5 inches for adults. Once fully inserted, stabilize the syringe with your non-dominant hand to prevent movement and discomfort.
While historical practice included aspiration (pulling back on the plunger to check for blood), current guidelines for most intramuscular injections, especially vaccines, generally do not recommend this step. This is due to a lack of evidence supporting its necessity and potential for discomfort. However, institutional policies may vary, so follow specific protocols. If aspiration is performed and blood appears in the syringe, the needle is likely in a blood vessel and should be withdrawn, discarded, and a new injection prepared.
If no blood is aspirated, or if not required, slowly and steadily inject the medication by pressing down on the plunger. A recommended injection rate is approximately 10 seconds per milliliter, allowing muscle fibers to accommodate fluid and reducing leakage. Once medication is injected, leave the needle in place for about 10 seconds to allow it to disperse within the muscle tissue. After this pause, remove the needle quickly and smoothly at the same 90-degree angle at which it was inserted.
After the Injection and Important Safety Warnings
After withdrawing the needle, apply firm pressure to the injection site with a clean gauze pad or cotton ball for 30 seconds to 1 minute. This minimizes bleeding and bruising. A small bandage can be applied if needed. Mild soreness, redness, or bruising at the injection site are common and generally resolve within a few days, a normal response.
Proper disposal of used sharps prevents accidental needlestick injuries and infection spread. Never recap a used needle. Immediately place the entire syringe and needle into a puncture-resistant sharps container. This container should be heavy plastic or metal with a tight-fitting lid (e.g., a designated medical sharps container or heavy-duty laundry detergent bottle). Ensure needles point down and the container is not overfilled.
When full, follow local regulations for disposal (e.g., returning to a pharmacy or designated collection station). Other used supplies, like alcohol swabs and gauze, can typically be discarded in regular trash. After disposing of all materials, wash your hands thoroughly again.
Understand the risks associated with intramuscular injections. While generally safe when performed correctly, improper technique can lead to complications.
Potential Complications
Improper technique can lead to nerve or blood vessel damage, causing severe pain or even paralysis. Localized infections, including abscesses, can occur if aseptic technique is not followed. Seek immediate medical attention if you experience severe or worsening pain, spreading redness, significant swelling, warmth, pus or clear fluid draining from the site, or red streaks spreading from the area, as these could indicate an infection. A fever higher than 100.4°F (38°C) after an injection should prompt medical consultation.
Allergic Reactions
Be alert for signs of an allergic reaction: widespread rash, severe itching, hives, or difficulty breathing. Call emergency services immediately if these occur.
This information is provided for educational purposes only and is not a substitute for professional medical advice or hands-on training from a healthcare provider.