Influence of needle size for subcutaneous insulin administration on metabolic control and patient acceptance

Aim: To investigate whether the length of the needle used for intermittent subcutaneous insulin administration affects metabolic control, injection-related side effects and patient preference.Method: In a crossover study, 68 patients with type 1 and type 2 diabetes, body mass index ≥ 18 kg/m2, were randomised into two groups; 52 patients completed the trial. Patients in group A used a 5 mm needle for their insulin injections over a period of 13 weeks, then switched to a longer needle (8 or 12 mm). Patients in group B used the needles in reverse order. Patients were re-assessed at 26 weeks. Primary endpoints were insulin doses, and frequency and severity of hypoglycaemic events. Secondary endpoints were patient preference and frequency of injection-related bruising, bleeding, insulin leakage and pain.Results: A total of 52 patients completed the study. No change in the mean glycosylated haemoglobin (HbA1c) level was found in group B (baseline, 7.41%; 13 weeks, 7.38%; 26 weeks, 7.34%), whereas a small but significant rise in mean HbA1c level was observed in group A after returning to the longer needle (baseline, 7.67%; 13 weeks, 7.65%; 26 weeks, 7.87%: p<0.05). There were no significant changes in the amount of insulin injected, frequency or severity of hypoglycaemic events or insulin leakage in either group. The 5 mm needle was associated with a significant decrease in bleeding, bruising and pain (p<0.05). Most patients (86%) showed a preference for the 5 mm needle (p<0.05).Conclusion: For insulin injection, a 5 mm needle length is associated with unchanged HbA1c levels, unchanged frequency or severity of hypoglycaemic events and less discomfort for patients compared with 8 or 12 mm needles. The use of 5 mm needles is as safe as 8 or 12 mm needles. Further research is advisable involving thin and obese patients using 5 mm needles, in order for shorter needles to be recommended as standard practice.