Bruising (BR) is a poorly investigated skin complication of improper insulin injection habits

BR is often associated with lipohypertrophy (LH) at the injection sites, but can also occur separately

BR does not correlate with factors associated with LH and does not modify the pharmacokinetics and pharmacodynamics of insulin; therefore, BR is not associated with the rate of hypoglycemic events and the extent of glycemic variability

BR most likely depends on a hard pen pressure onto the skin, a habit commonly observed in people made insecure by unconscious injection fear

BR is the consequence of an injection technique error and may represent an early stage of LH, thus requiring a more effective prevention through sustained structured education