I usually stick the needle roughly four inches under my belly button and a couple inches off to each side. Trying the spot right around the navel always gave me a sharp sting like a pellet from an air rifle. Shifting down a bit makes the whole thing way gentler. I ordered the injector pens originally because I wanted to place the copper peptide into my rear, yet twisting around with a standard insulin syringe seemed impossible. Once the pens showed up I realized the lower spot hurt less anyway, so I just go there now. An extra benefit is that I mix the peptide into both the original bottle and the pen cartridge using three more milliliters of sterile water, which seems to cut down the burn. I start by adding three milliliters to the powder, pull out half of that into the cartridge, then add another three milliliters and divide it evenly. That leaves one hundred milligrams spread through six milliliters total. Not sure if it works better overall, but at least the sharp pain is gone. Regarding the question about strange reactions, nothing unusual turned up with the peptide itself. The main change is that my skin feels tougher and more elastic, and folks mention the lines on my face look softer. I also stir collagen powder into my morning coffee, do some needling sessions, and rub on a four percent cream version. The loose skin under my chin is still there though.