Insulin Injection Behaviors and Association with Glycemic Outcomes in Patients with Diabetes: A Real-World Survey in Spain

INTRODUCTION: Optimal glycemic control is essential to prevent complications in diabetes, and insulin administration practices play a key role. This study assessed insulin injection behaviors and related glycemic outcomes among individuals using multiple daily injections in Spain. METHODS: A cross-sectional online survey was conducted via an independent patient platform (Canal Diabetes). Adults (18-65 years) with type 1, type 2, or other forms of diabetes (e.g., maturity-onset diabetes of the young (MODY) or secondary diabetes) requiring daily insulin injections were included. Demographic, clinical, and behavioral data were analyzed using SPSS Statistics, version 23 (IBM Corp., Armonk, NY, USA). RESULTS: Among 288 participants (mean age: 43.7 ± 14.7 years; 28.8% male, 71.2% female), 74.7% had type 1 diabetes. Most were white (95.8%) with a mean diabetes duration of 17.8 ± 14.5 years. While 83.3% injected prandial insulin before meals, only 71.2% did so at least 15 min before eating. Errors were frequent: 38.5% reported underdosing and 26.7% overdosing more than five times in the past month. Participants injecting before meals had significantly better outcomes than those injecting at other times, including higher rates of glycated hemoglobin (HbA1c) ≤ 7.5% (83.3% versus 62.5%, p = 0.001), greater time in range (TIR) (74.4% versus 66.3%, p = 0.032), and lower mean glucose (144 versus 159 mg/dL, p = 0.019). Smart pen users (41.2%) reported fewer mild-to-moderate hypoglycemic events (p = 0.021), though no differences were observed in HbA1c or TIR. CONCLUSION: Insulin injection practices in Spain reveal significant variability and opportunities for improvement. Promoting timely premeal insulin administration and leveraging technologies such as smart pens may improve glycemic outcomes. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT06421467.