To date, there has been a shortage of randomised prospective studies to establish the causative factors of lipohypertrophy. Observational studies suggest a link between lipohypertrophy and a failure to rotate injection sites, repeatedly injecting into the same zone within an injection site and the reuse of needles. In a Spanish study, Blanco, Hernandez, Strauss and Amaya examined the prevalence and risk factors of lipohypertrophy in people who inject insulin. The study found that almost two thirds of people had lipohypertrophy (76.3% of those with type 1 diabetes, and 56.1% of those with type 2 diabetes), and this was strongly associated with a failure to rotate injection sites. The correct rotation of injection sites was the strongest protective factor against the development of lipohypertrophy. Only 5% of people who rotated correctly developed lipohypertrophy.15 Needle reuse was identified as another causative factor of lipohypertrophy, and the risk rose significantly when needles were used more than five times.15
Glycaemic variation occurred in 49% of people with lipohypertrophy, compared to 6.5% in those without it. On average, people with lipohypertrophy required 56 units of insulin per day, compared to 41 units for those without it. Blanco Hernandez, Strauss and Amaya calculated that the 15-unit difference in the total daily dose of insulin equated to an annual additional cost of €122 million to the Spanish health system, and suggested that potential cost savings could be made if insulin doses were reduced. More importantly, addressing poor injection technique would improve the quality of life of patients using injectable therapies as less glycaemic variability leads to fewer diabetes- associated complications.