Ten insulin-dependent diabetic patients were investigated from 2100 to 0700 h during treatment with either a bedtime injection (BI) of intermediate-acting insulin or continuous subcutaneous insulin infusion (CSII) at a constant basal rate. In the evening, blood glucose was slightly higher during treatment with BI than with CSII, whereas the metabolic control in the morning was equal on both regimens with a fasting blood glucose of 5.7 mM (4.2–7.1) (median and interquartile ranges) on BI and 5.4 mM (4.6–5.8) on CSII (NS). No rise in morning blood glucose was seen, but serum β-hydroxybutyrate tended to rise (NS). There was a significant hyperinsulinemia at midnight during BI compared with CSII with a serum free insulin of 14.5 (11.7–16.0) vs. 9.6 (7.2–11.2) mU/L (P < .05), respectively, and the area under the curve during the middle of the night (midnight to 0400 h) was greater with BI than CSII (P < .02). A greater fall in blood glucose was seen with BI than with CSII during this period (P < .02). Differences in blood glucose and serum free-insulin profiles between those using NPH or lente insulin at bedtime were registered. We conclude that, although the same metabolic control in the morning was achievable with CSII at a constant basal rate and BI, CSII is superior for overnight metabolic control due to less-pronounced hyperinsulinemia during the night and a steady-state level of free insulin in the morning.

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