How-to: Subcutaneous injection

What is a subcutaneous “Sub-Q” injection?

A subcutaneous injection is a method of administering medication. Subcutaneous means under the skin.

In this type of injection, a short needle is used to inject a drug into the tissue layer between the skin and the muscle. Medication given this way is usually absorbed more slowly than if injected into a vein, sometimes over a period of 24 hours.

This type of injection is used when other methods of administration might be less effective. For example, some medications can’t be given by mouth because acid and enzymes in the stomach would destroy them.

Preparing for a Sub-Q injection:

The location of injection is important for subcutaneous injections. The drug needs to be injected into the fatty tissue just below the skin. Some areas of the body have a more easily accessible layer of tissue, where a needle injected under the skin will not hit muscle, bone, or blood vessels.

The most common injection sites are:

Equipment used for subcutaneous injections includes:

Medication: Vials of liquid medication can be single-use or multiuse. Vials can also be filled with a powder to which liquid needs to be added.

Syringes: The needles are short, at 5/8 inches long. The thickness of the needle is usually 25 or 27 gauge. There may be other options for doses more than 1 mL or for children or people with visual impairments.

Auto-injector pen: Some medications are available in a “pen” with a short single-use needle screwed onto the end of a pen-shaped, multiuse vial. The amount of medication needed is then dialed in at the end. As mentioned earlier, emergency medications like epinephrine can also come in this form.

How to administer a subcutaneous injection:

Wash your hands. Wash your hands with soap and warm water to prevent potential infection. Be sure to thoroughly scrub between fingers, on the backs of hands, and under fingernails. The Centers for Disease Control and Prevention (CDC) recommends lathering for 20 seconds — the time it takes to sing “Happy Birthday” twice.

Assemble the following supplies: Needle and syringe with medication or auto-injector pen, alcohol pads, gauze, puncture-resistant container to discard the used needles and syringe (typically a red, plastic “sharp’s container”), bandages

Clean and inspect the injection site. Before injecting medication, examine your skin to ensure no bruising, burns, swelling, hardness, or irritation in the area—alternate injection sites to prevent damage to an area with repeated injections. Then you should clean the skin with an alcohol swab. Let the alcohol dry thoroughly before doing the injection.

Prepare the syringe with medication. Before withdrawing medication from a vial and injecting yourself or someone else, make sure you’re using the correct medicine, at the correct dose, at the proper time, and in the right manner. Use a new needle and syringe with every injection.

Preparing a syringe:

1. Remove the cap from the vial.

If the vial is multidose, make a note about when the vial was first opened. The rubber stopper should be cleaned with an alcohol swab.

2. Draw air into the syringe.

Draw back the plunger to fill the syringe with air up to the dose that you’ll be injecting. This is done because the vial is a vacuum, and you need to add an equal amount of air to regulate the pressure. This makes it easier to draw the medication into the syringe. Don’t worry, though — if you forget this step, you can still get the medication out of the vial.

3. Insert air into the vial.

Remove the cap from the needle and push the needle through the rubber stopper at the top of the vial. Inject all the air into the vial. Be careful to not touch the needle to keep it clean.

4. Withdraw the medication.

Turn the vial and syringe upside down so the needle points upward. Then pull back on the plunger to withdraw the correct amount of medication.

5. Remove any air bubbles.

Tap the syringe to push any bubbles to the top and gently depress the plunger to push the air bubbles out.

6. Pinch your skin.

Take a big pinch of skin between your thumb and index finger and hold it. (Your thumb and forefinger should be about an inch and a half apart.) This pulls the fatty tissue away from the muscle and makes the injection easier.

7. Inject the needle.

Inject the needle into the pinched skin at a 90-degree angle. You should do this quickly, but without great force. If you have very little fat on your body, you may need to inject the needle at a 45-degree angle to the skin.

8. Insert the medication.

Slowly push the plunger to inject the medication. You should inject the entire amount of medication.

9. Withdraw the needle.

Let go of the pinched skin and withdraw the needle. Discard the used needle in a puncture-resistant sharp’s container.

10. Apply pressure to the site.

Use gauze to apply light pressure to the injection site. If there’s any bleeding, it should be very minor. You may notice a little bruising later. This is common and nothing to be concerned about.

Complications of subcutaneous injection:

If you are doing this type of injection for more than one dose or multiple days, you’ll need to rotate the injection sites. This means that you shouldn’t inject medicine into the same spot twice in a row.

For example, if you injected medicine into your left thigh this morning, use your right thigh this afternoon. Using the same injection site repeatedly can cause discomfort and even tissue damage.

As with any injection procedure, infection at the site of injection is possible. Signs of infection at the injection site include:

severe pain
redness
swelling
warmth or drainage

These symptoms should be reported to your physician immediately.