Is there some formal guide for conversion of insulin from a drip rate to Lantus? If a ICU patient is receiving approximately 75 units of Regular per day, and the attempt is being made to convert from drip to Lantus, how much Lantus would be given?

We will frequently use the total intravenous insulin dose to make some determinations about a subcutaneous insulin schedule. If there was someone who required 75 units over 24 hours, you would take roughly half that and use as long-acting insulin and the other half as short-acting insulin divided into three meals. Therefore, 75 divided by 2 is 37.5 units. You could give 37 units as Lantus and roughly 12 units of short-acting insulin per meal. However, there is an additional issue here. Lantus takes three to five days to get on board and effectively provide basal insulin. You cannot rely on the Lantus to be there 24 hours after the insulin drip is stopped.

I would recommend switching to NPH insulin as the long-acting insulin of choice immediately following the IV insulin. You can switch to Lantus from NPH in the outpatient setting, if that is your choice.

JTL

[Editor’s comment: Assuming the patient will remain in the hospital for several days, you could use the NPH in three equal doses every eight hours to get a feel for how much basal insulin is needed (plus boluses of your favorite short-acting insulin analog at mealtime), then switch to Lantus later. The advantage to the Q8H NPH dosing is the ability to rapidly titrate doses in what inevitably is an unstable setting.

WWQ]