When switching from NPH to Lantus, how should the dosage be adjusted for BID NPH?

When switching from NPH to Lantus, it is essential to understand the pharmacological differences and the dosing schedules of these two insulins. NPH (Neutral Protamine Hagedorn) is an intermediate-acting insulin that is typically administered twice daily, while Lantus (insulin glargine) is a long-acting insulin used once daily.

The reason for reducing Lantus by 20% when transitioning from BID NPH is based on Lantus's pharmacokinetics and the fact that Lantus provides a more stable and continuous level of insulin throughout the day compared to the peaks and valleys associated with NPH. NPH has a pronounced peak effect, which can lead to a higher total daily dose to achieve similar blood glucose control due to its shorter duration of action.

When approximating the dose conversion, a common practice is to reduce the daily dose of basal insulin when switching to a long-acting insulin like Lantus to mitigate the risk of hypoglycemia. This reduction accounts for the differences in insulin action and helps ensure that blood glucose levels remain stable without causing the patient to experience low blood sugar levels during transition. Therefore, adjusting the Lantus dosage down by 20% helps provide a