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