Use the thinnest needle practical (30-31 gauge), let the peptide warm to room temperature for a few minutes before injecting, inject slowly, and avoid areas with visible veins. Icing the site briefly beforehand can numb the skin. Bruising is usually harmless and caused by nicking a small blood vessel—pressing firmly with a cotton ball or gauze after withdrawing the needle helps. If you're bruising frequently, try a different injection site or check whether you're on blood thinners or fish oil, which can increase bruising.