Basal insulin is titrated upward whenever the average of several days’ FG exceeds a goal. It is assumed that averaging better reflects the ‘true’ FG (Central Limit Theorem) but this is true only if they are normatively distributed. There are a large subgroup of patients with diabetes in which their day-to-day FG variation is not normative but characterized by intermittent large positive spikes, the “Hyper-Spikers,” and large coefficient of variability (CV). We report their prevalence and characteristics in a large clinical practice. From 2000+ clinic charts, the data from 200 charts were consecutively selected if the patients had T2DM and were on basal insulin ± non-insulin but no bolus insulin. Only those with ≥ 3 consecutive daily FG readings were selected. CV = (SD/mean)*100. Hyper-Spikers were arbitrarily defined as a day to day FG CV ≥ 20%. CV distribution of the FG sets for all patients was not normative distributed but positive skewed with a mean CV of 17.8% and median, 15.9%. CV sets were divided into those ≤ 10% (LoVar) vs. those, ≥20% (Hyper-Spikers), 29 and 32% of patients, respectively. Age, gender, DM duration and weight were not different between groups (p > 0.20). The mean basal doses were 23.1 vs. 30.0 U/d (p=0.0157) and 0.247 vs. 0.327 U/kg (p=0.00153) yet the A1c was higher, 8.06 vs. 8.47% (p = 0.0951) in Hyper-Spikers. The correlation coefficient of all individual’s CV at baseline vs. a mean follow-up of 4.1 m was 0.197 (p = 0.0166). From these observations, the Hyper-Spikers are not significantly different in age, gender, diabetes duration and weight from LoVar. The Hyper-Spikers were treated to a significantly higher basal insulin dose yet had a more elevated A1c. We conclude that the traditional method of averaging FGs to determine dosage increase is misleading in a significant (1/3) portion of patients and may lead to excessive basal insulin. We recommend that Hyper-Spikers be identified and the cause of the spikes determined before the dosage is increased.


A.B. King: None.

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