Why does the same injection spot get a lump?

The lump is lipohypertrophy, a buildup of fatty tissue from repeated trauma to the same small patch of skin. A 2026 meta-analysis pooling 51 studies of people on insulin therapy found incorrect site rotation was the strongest measured risk factor, with roughly nine times the odds compared with proper rotation, ahead of reusing the same needle. The lump itself absorbs medication more slowly and less predictably than normal tissue. Full detail at /injecting.

Educational use only. This database summarizes published research and is not medical advice. Where a dose appears it is a record of what a trial or clinic ran, or what people describe doing, with its source attached. Nothing here is a recommendation for personal use.

Part of injecting: sites, needles and safety. Subcutaneous vs intramuscular, where people inject, rotation and lipohypertrophy, needle gauge, aseptic technique, why it stings, and sharps disposal. Full walkthrough at /injecting.