The short insulin tolerance test (ITT) is both a simple and valid meth
od of quantifying insulin sensitivity although arterialization of samp
les and the risk of hypoglycaemia remain as potential difficulties. We
examined the safety and reproducibility of using venous sampling with
insulin doses of 0.1 U kg(-1) and 0.05 U kg(-1) in healthy subjects.
Whole blood glucose concentrations were measured contemporaneously and
the rate of plasma glucose decline (mmol l(-1) min(-1)) for each test
was estimated from unlogged venous plasma glucose concentrations meas
ured at 1 min intervals. The mean rates of plasma glucose decline for
the O.1 U kg(-1) and 0.05 U kg(-1) insulin doses were 0.26 mmol l(-1)
min(-1) (n=11, range=0.17-0.41, intrasubject coefficient of variation
(CV)=9.4%) and 0.25 mmol l(-1) min(-1) (n=6, range 0.19-0.46, intrasub
ject CV=15.9%), respectively. Reversal of significant hypoglycaemia wa
s necessary in one subject before 15 min post-insulin. We found that:
(1) venous sampling provides a reproducible measure of glucose uptake
after insulin, (2) contemporaneous bedside glucose sampling identifies
those at risk of significant hypoglycaemia during the ITT, and (3) th
e 0.1 U kg(-1) dose response is more reproducible and no less safe tha
n the half dose response. We conclude that the current ITT protocol wo
uld be made safer and simpler with the above modifications although fu
rther studies comparing venous with arterialized sampling are needed.