How to Administer Injectable Medication to a Cat
Before administering an injectable medicine to your cat, let the medicine sit at room temperature for about 30 minutes to let it warm up, which makes the injection more comfortable. Next, open a sterile syringe and draw the prescribed dose of medication into it. Before injecting your cat, lightly tap the syringe against the counter to make any air bubbles come to the surface and press slightly down on the plunger to eliminate them. Then, ask someone to hold the cat or wrap it in a blanket to keep it from running away or scratching you. Finally, pull up the scruff of your cat's neck and inject the medicine between the folds of its skin.
Talk to your vet. Injectable medications are almost always prescribed by a vet, and it is a good idea to do a training session with your cat's vet on how to properly administer the medication. Ask your vet to show you how to properly load the syringe, and have them walk you through where and how to inject the medication. It is also advisable to ask your vet about any aftercare needed for the injection site. Typically, injection sites just need to be carefully monitored, but your vet may also recommend further care depending upon the medication being used. If you feel nervous or unprepared to administer this injection, do not be afraid to ask your vet for additional training. It is part of their job to help you get comfortable enough giving the injection that you can do it properly and pose minimal risk to yourself or your pet. Ask your vet to supply you with needles and syringes so that you can practice at home. You can practice by injecting water into fruit. This will help you learn how to manipulate the syringe. Warm the injection. Cold injections often hurt. If you are providing and injection of medication that is stored in the fridge, take the medication out and allow it to warm up for half an hour or so before injecting. Do not warm up medication in the microwave or on the stove. This could impact the medication's effectiveness, and also has the potential to hurt your cat. Restrain your cat. Many cats do not mind routine injections, as the needle point is kept very sharp to minimize discomfort. However, if your cat tends to dislike being handled, or if they become aggravated when they get a shot from the vet, it may be a good idea to calmly and gently restrain your cat. If your cat is comfortable sitting on your lap for the injection, remember to place a towel or blanket across your legs to help keep you from getting scratched. It may be helpful to have a second person hold the cat, protecting themselves with a blanket, while you administer the medication. This way, you do not have focus on restraining the cat while you provide the injection. You may also be able to distract your cat with a small treat such as canned food during the injection process. Prepare a sterile injection. Each needle and syringe is sterile until it is removed from its packaging, as is the medication. Prepare the injection so that you are ready to give it as soon as the syringe is filled, and avoid putting it down on counters or other potentially unclean surfaces. To prepare the injection, place the needle tip into the medication and pull back the plunger of the syringe until you have taken up the recommended dose. A sterile syringe and needle should be used for every injection. If you are unclear about the recommended dose, check the medication packaging or call your vet. Check the syringe for air bubbles. Tap the barrel of the syringe to cause any air bubbles that you don't see to rise up to the surface. Gently press the plunger to eliminate the air from the syringe. Never inject air into your pet, as this will harm them. Pull up the scruff of the neck. Subcutaneous injections are the most common injection that owners will have to administer to their cat, and most subcutaneous medications can easily be administered directly into the folds of skin around the cat's neck. If you are giving a subcutaneous injection, gently pull the scruff of the neck upward so that it is sticking up like a small pyramid. Hold the skin in place between your thumb and index finger while you inject. Subcutaneous injections are the most common, but they are not the only type of injection a pet owner may be asked to give. Different types of injections have different injection sites. If you are not sure what type of injection you are administering, contact your vet for verification. If you are not giving a subcutaneous injection, simply locate the injection site your vet showed you. Make sure it is clear of any debris or matting before injecting. Give the injection. When your cat and its skin are in place, quickly insert the needle into the skin at about a 45 degree angle. Depress the plunger to inject the medication, and withdraw the needle from the skin as soon as the medication has been administered. It is important to administer the medication quickly, but not in such a rush that you are not able to do so properly. Do not feel so rushed that you panic and fail to perform the injection properly. It is ok to take a few seconds to fully administer the injection. Dispose of the needle and syringe. Place the needle guard back over the needle before disposal. Collect the used needles and syringes in a plastic container with solid walls and a sealable lid. Place all used needles and syringes in this container, and don't forget to reseal it after disposing. Keep the container some place secure, out of reach from children and pets, and away from an area where it could fall over or get knocked down on someone. As the container fills, take the used needles and syringes to your vet or a nearby pharmacy for disposal. Most communities have strict regulations regarding medical waste, prohibiting you from simply throwing the old needles in the trash. Massage the site after injection. After you administer the injection, use the pads of your fingers to gently massage the injection site for a minute. This applies gentle pressure to the area to stop any small amounts of bleeding that may occur due to the injection. If your cat is sensitive after an injection, it is alright to let them go without massaging the injection site, so long as they are not bleeding profusely or uncontrollably. If you notice your cat bleeding excessively after injection, contact your vet or a nearby animal hospital immediately. Give your cat love and praise. After injection, be sure to give your cat affection and praise for any good behavior. Reward them with scratching or petting, and perhaps a treat. This is especially important for cats who receive regular injections, such as insulin, as it helps them associate the experience with positive outcomes. Monitor the site. After injection, be sure to monitor the site for any swelling, excessive bleeding, discoloration, leaking medication, or excessive tenderness. If you notice any of these complications arising, contact your vet immediately, as it may be an indication of a bad injection or a negative reaction to the medication. Try not to inject your cat in the exact same location every day, as this may cause soreness or tenderness. Find a few different spots within the prescribed injection site, and rotate injecting in each of them so that the others have the chance to heal. 
Talk to your vet. Warm the injection. Restrain your cat. Prepare a sterile injection. Check the syringe for air bubbles. Pull up the scruff of the neck. Give the injection. Dispose of the needle and syringe. Massage the site after injection. Give your cat love and praise. Monitor the site. 