Injecting your cat with medicine is probably the least fun way to follow doctor's orders, since most likely it's required on a continual basis. Diseases such as diabetes or allergies often require injectable medications but following your vet's guidelines will help ensure that your cat is happy and healthy for a long time.
Injectable medications can be prescribed for either subcutaneous or intramuscular use. Most medications that veterinarians dispense for owners to give at home are for subcutaneous use. Discuss the proper route and technique with your veterinarian prior to administering the medication at home.
For drugs that can be administered via subcutaneously, you can try this method:
Remember, if you feel uncomfortable administering injectable medication; discuss other alternatives with your veterinarian. If you are having difficulty, call your veterinarians office and ask if you can stop by and have the veterinarian or one of the technicians' demonstrate the technique for you.
Here's a tip that has worked for some pet owners - If you don't want to take your pet in, you can sometimes practice with the medication and syringe on a piece of frut such as an orange or banana.