Read the instructions on a veterinary product; know the type of injection technique required and the correct size of needle to use. Injection equipment should be clean and sterile. Reduce contamination — keep a sterile needle in the bottle to refill the syringe and a different needle to inject. If you are injecting a number of pigs, change needles after every five to 10 pigs. Safely restrain pigs. Note any withdrawal period — the time between the last dose of medicine administered and the time when it is safe to enter the food chain. Record everything in your medical records book.