There are a number of ways to do an injection. HCG is a fragile molecule and needs to get into the system quickly to be happy and to be able to do its job. If injected into the tummy or fat layer, it can linger too long and begin to degrade and become less effective. There is less circulation in the fat layer, therefore a little higher dose may be required. Dr. Simeons recommended injecting into the muscle for the best results.
Using an insulin syringe which is a very tiny needle, it really doesn't hurt. Not much more than pinching the skin. Not all spots are created equal. Place the needle to the skin and press.... if it stings then move over an 1/8th inch and see if that feels better. I look for the whitest spot.... that seems to have less nerve endings.
Always wipe the skin with the alcohol prep to disinfect the area.
