The basal insulin dose; a lesson from prolonged fasting in young individuals with type 1 diabetes

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Background and objective:

The insulin requirement for type 1 diabetes during prolonged fasting is unclear. In order to define this for clinical purposes, we investigated the total insulin dose associated with successful completion of a 25 h religious fast.

Subjects and methods:

Questionnaires were filled in during telephone interviews performed before and after 88 fasts in 57 young individuals with type 1 diabetes (age 20.4 ± 5.3, range: 12.3–31.2 yr). Duration of their diabetes was 8.7 ± 6.1 yr (range: 0.5–21.8) and latest HbA1c was 8.5 ± 1.9% (5.7–13.7). Twenty-eight patients fasted using multiple daily injections (MDI) and 30 were on continuous subcutaneous insulin infusion (CSII), including one who fasted in both categories. Subjects were instructed either to act as they had done for previous successful fasts or, for first-time fasts, to inject half their daily basal insulin injection or halve their basal CSII rate throughout the fast. The total daily insulin dose associated with successful completion of the fast was determined.


Among those who completed the fast, average total insulin was 0.19 ± 0.16 U/kg, patients who discontinued their fast took on average 0.34 ± 0.15 U/kg. Seven MDI patients and 12 CSII patients terminated their fast early, mostly for mild hypoglycemia. No severe hypoglycemia or other serious adverse event occurred during any of the fasts.


Fasting for 25 h is safe and can be undertaken in individuals with type 1 diabetes. The recommended total daily dose is 0.2 U/kg/day. This recommendation may possibly be used for other situations in which abstention from oral intake is required.

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