Some improvements in diabetes care happen slowly, whereas others seem to happen very fast. For a number of reasons, in the last two years we have suddenly seen a dramatic change in our approach to insulin therapy. This has partly been due to the roll-out of continuous and flash glucose monitoring. This, combined with the enforced inability to see people face to face, meant we had to develop tools for remote monitoring and has resulted in a dramatic increase in data sharing between people with diabetes and clinicians, particularly with regard to glucose levels throughout the day. Instead of a meeting where a paper glucose diary with perhaps two to four readings per day is reviewed, we now have a wealth of detail about day-to-day glucose variation.

This change has shifted the conversation in clinic and, as we know, resulted in measurable improvements for the individual with diabetes. It does, however, highlight a gaping hole in the information that we need in order to give accurate advice: we know very little about the appropriateness and timing of insulin doses. At the moment, the information we have for an individual using insulin pump therapy will be very different to that available for a person using multiple daily injections of insulin. Often we can only assume that insulin has, firstly, been taken and, secondly, been taken at an appropriate time and dose for that meal. Evidence would suggest that this assumption will be incorrect for a relatively high proportion of the time.

This paper by Susan Robinson and colleagues, reviewed below, summarises our current knowledge about the timing of insulin injections for people with both type 1 and type 2 diabetes. The results are sobering but perhaps not surprising, with one or two doses of insulin being missed per person per week. The timing of bolus insulin in relation to meals is also important and, while we often assume in the clinic that the dose is being taken at the right point, the data would suggest this is probably not the case around 50% of the time.

These are the basics of insulin self-administration that we mostly assume are understood and practised correctly before considering factors such as matching the insulin dose to the carbohydrate content of the meal, the proportion of the previous insulin injection still active, correction doses to manage the current glucose level and the effects of previous or planned physical activity. When there is a problem with glucose control, we often assume it is these complexities that need addressing, without considering that just remembering to take the insulin correctly may be a challenge.

Technology is already helping, with automated systems to help calculate insulin doses and smart pens to remind about insulin injections, but in addition the consultation needs to evolve to deal with this new conversation. To best help the person with diabetes, we need to match the wealth of glucose data with equally accurate measures of insulin dose and timing. Hopefully this will come in the near future.

Article summary

Prevalence and effects of missed and mistimed insulin doses

This systematic review was conducted to assess the extent and consequences of missed and mistimed insulin doses in people with diabetes. A total of 30 studies involving 58617 people with diabetes were included.

Between 12% and 56% of participants with type 1 diabetes had missed one or more insulin dose in the previous month, while 16–23% of people with type 2 diabetes had. Among the latter group, those who were on a basal–bolus regimen were more likely to miss insulin doses compared with those on premixed or basal insulin regimens.

Missed insulin doses were consistently reported to be associated with higher HbA_1c, whilst in one study of people with type 2 diabetes, missing around 3–4 basal insulin doses per month resulted in significantly worse glycaemic control. Missed insulin doses were associated with lower health-related quality of life in adolescents with type 1 diabetes and in adults with type 2 diabetes.

Regarding mistimed insulin doses, around 25–30% of people with diabetes (type 1 or type 2) administered their bolus insulin during or after meals, contrary to guidelines, while around 20–26% had mistimed their basal doses in the previous 30 days. Hypoglycaemia was more common in people who took their bolus insulin after meals compared with before or during, and glycaemic control was better in those who took their bolus doses regularly and before meals.

Reasons for missing or mistiming insulin included forgetfulness, disruption to routines (including travelling), obstruction of usual daily activities, fear of hypoglycaemia, stress (including diabetes distress and burnout), injection pain, and embarrassment in public or social situations. Regimen complexity and the challenges of taking insulin at the same time each day were also cited as reasons.

The authors conclude that some individuals continue to struggle with the complexities of diabetes management and the specific challenges of insulin therapy. Approaches that facilitate better diabetes management are needed.