Injection-meal interval: recommendations of diabetologists and how patients handle it

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Abstract

Because regular insulin does not lower blood glucose immediately after injection many physicians recommend an injection-meal interval (IMI). By asking patients to inject well before beginning a meal, these physicians hope to compensate for the lag time between the injection of insulin and its onset of action. The aim of our study was to find out what physicians recommend to their patients with respect to the IMI, when prescribing intensive insulin therapy. A total of 58 diabetologists were surveyed by means of a structured questionnaire. A fixed IMI of 15 (0–30) min [median (range)] was recommended by 29% of the 58 diabetologists, and a flexible IMI was recommended by 71%. The minimal interval for the suggested flexible IMI was 0 min and the maximal interval 45 min (median 23 min). We compared these results with findings of 192 patients with Type 1 diabetes from a population based study. In this study patients were asked by questionnaire about their daily life handling of the IMI. Among the group of 134 patients reporting use of a flexible IMI, 62% used an IMI of ≤15 min, 16% one of 20–25 min, and 21% one of ≥30 min. There were 12 patients using a flexible IMI who adapted it so frequently that they could not state a typical interval. A total of 58 patients (30%) used a fixed IMI (67% used an IMI of ≤15 min, 7% one of 20–25 min, 26% one of ≥30 min). Our surveys show that diabetologists advocating intensive insulin therapy usually recommend an IMI shorter than 30 min. The majority of patients (75%) with Type 1 diabetes use an IMI of <30 min in daily life.

Introduction

To compensate for the delay between onset of action of human regular insulin following injection into the subcutaneous tissue (i.e. delayed absorption from the subcutaneous depot) and the rapid postprandial absorption of carbohydrates, a time interval of 30 min between the injection of prandial insulin and start of the meal is often recommended to patients. The rational behind the injection-meal interval (IMI) is to allow enough time for insulin absorption from the subcutaneous depot so that insulinaemia is adequate before glucose absorption begins after a meal, thereby limiting the postprandial blood glucose excursions. However, recommendations for the IMI resulting from clinical experimental studies vary considerably between 0 and 90 min [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]. In our department the use of an IMI of more than 15 min is not recommended [13]. Many experienced diabetic patients do not use a fixed IMI but a flexible one, modifying the interval depending on the preprandial glycaemia (i.e. a longer interval if glycaemia is elevated) [4], [14], [15]. Overall our knowledge about the use of IMI by diabetic patients is poor [16].

The aim of our study was to evaluate: (i) what suggestions diabetologists give to their diabetic patients treated with intensified insulin therapy; and (ii) how diabetic patients handle such recommendations in daily life. Therefore we asked a group of German diabetologists about the recommendations given with respect to the IMI. In a different survey we asked 202 randomly selected patients with Type 1 diabetes mellitus from one geographical area in Germany about their use of the IMI under daily life conditions.

Section snippets

Patients and methods

In July 1996 we submitted a structured single page questionnaire to 72 diabetologists who are organised in the ‘Arbeitsgemeinschaft Strukturierte Diabetestherapie’ (Working Group for Structured Diabetes Therapy) of the German Diabetes Association. Most of these physicians are specialised in diabetes treatment. The questionnaire contained items with respect to the use of the IMI, the suggested intervals and conditions which influence the choice of the interval when using a flexible IMI. (The

Diabetologists

Of the 72 diabetologists, 58 (81%) returned the questionnaire. A fixed IMI of 15 (0–30) min was recommended by 29% of the diabetologists, whereas 71% recommended a flexible IMI. The median of the minimal intervals reported was 0 min and of the maximal intervals 45 min (median of all mean intervals 23 min) for the flexible IMI, with considerable differences between physicians (Fig. 1a; results from 35 colleagues responding to this question). The greatest impact on the choice of the IMI was

Discussion

Our study shows that a large proportion of diabetologists practising intensive insulin therapy in specialised hospitals (>70%) recommend the use of a flexible IMI to their patients. Of the Type 1 diabetic patients asked 70% use a flexible IMI. In accordance with the considerable differences in the intervals suggested by the diabetologists asked, the IMIs reported by the diabetic patients differed widely. Overall both were in the same range. More than 60% of the patients reported that during

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