When a medication is injected directly into muscle, it is called an intramuscular injection (IM). The Z-track method is a type of IM injection technique used to prevent tracking (leakage) of the medication into the subcutaneous tissue (underneath the skin).
During the procedure, skin and tissue are pulled and held firmly while a long needle is inserted into the muscle. After the medication is injected, the skin and tissue are released. When you insert a needle into the tissues, it leaves a very small hole, or track. Small amounts of medication can sometimes leak backwards through this track and be absorbed into other tissues. Pulling the skin and tissue before the injection causes the needle track to take the shape of the letter “Z,” which gives the procedure its name. This zigzag track line is what prevents medication from leaking from the muscle into surrounding tissue.
The procedure is usually administered by a nurse or doctor. In some cases, you may be instructed how to perform Z-track injections on yourself at home. You may also need the help of a caregiver, friend or family member to administer the injection.
Side effects can include swelling and injection discomfort. However, Z-track injection is usually less painful than a traditional IM injection.
The Z-track method is not often recommended, but can be particularly useful with medication that must be absorbed by muscle to work. It also helps to prevent medication from seeping into the subcutaneous tissue and ensures a full dosage. Some medications are dark colored and can cause staining of the skin. If this is a side effect of the medication you will be taking, the doctor may recommend using this technique to prevent injection site discoloration or lesions.
Z-track injections can be performed at any intramuscular injection location, though the thigh and buttocks are the most common sites.
- Thigh (vastus lateralis muscle): Divide the upper thigh in thirds. Use the middle third, on the outside or middle of the muscle for the injection.
- Hip (ventrogluteal): Place the heel of your hand on the head of the greater trochanter (hip bone) with your thumb pointing toward the abdomen. Extend your index finger up to the anterior superior iliac spine then spread your other fingers back along the iliac crest. Insert the needle in the “V” formed between your index and third fingers.
It is important that the correct size needle is used. Your healthcare team will advise you on which needle and syringe to use, taking your weight, build, and age into consideration. You may also be asked about preexisting conditions. Be sure to tell your doctor if you have a bleeding disorder. In an adult, the most commonly used needles are one inch or one and a half inches long, and 22 to 25 gauge thick. Smaller needles are typically used when injecting a child.
- Wash your hands with soap and warm water. This will help 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 the “Happy Birthday” song twice.
- Gather the necessary supplies:
- needle and syringe with medication
- alcohol pads
- puncture-resistant container to discard the used needles and syringe (typically a red, plastic “sharp’s container”)
- Clean the injection site. Clean the injection site with an alcohol pad to minimize the possibility of infection. Allow the area to air dry for a few minutes.
- Relax the muscle to be injected. Get into a comfortable position so that your muscle is as relaxed as possible. This may be lying down on your stomach or bending over a chair or counter, or sitting (if self-injecting into your thigh).
- Prepare the syringe with medication.
- Remove the cap. If the vial is multi-dose, take a note about when the vial was first opened. The rubber stopper should be cleaned with an alcohol swab.
- Draw air into the syringe. Draw back the plunger to fill the syringe with air up to the dose that you will 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; if you forget this step, you can still get the medication out of the vial.
- 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.
- 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.
- 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.
- Insert the needle. Use one hand to pull downward on your skin and fatty tissue. Hold it firmly about an inch away (2.54 cm) from the muscle. In the other hand, hold the needle at a 90-degree angle and insert it quickly and deeply enough to penetrate your muscle.
- Inject the medication. If there is no blood in the syringe, push on the plunger to inject the medication slowly into the muscle.
- Create Z-track. Keep the needle in place for about 10 seconds before taking it out. After you’ve removed the needle, release your hold on the skin and tissue. This disrupts the hole that the needle left in the tissues and prevents the medication from leaking out of the muscle.
- Apply pressure to the site. Use gauze to apply gentle pressure to the site for a moment. A small bandage may be used if you are bleeding.
Note: Never massage the site of your Z-track injection. This may cause the medication to leak. It may also cause irritation.
Z-track injection is generally considered a common and safe procedure. Mild side effects include swelling, site pain, and bruising. Less common, but more serious risks include:
- formation of abscess
- infection – redness, swelling, warmth or drainage
- damage to tissues, nerves, blood vessels, or bones
- hemorrhage, especially in people with bleeding disorders
If you notice any unusual side effects or signs of an infection, promptly notify your physician.