Our daughter is on twice daily NPH with NovoLog, and, even though her doctor prescribed NovoLog, our pharmacy gave us Humalog. Around the time of the switch, it seemed like we had a few days of unexplained differences in blood sugars. When we asked her endocrinologist, he seemed indifferent, but the diabetes nurse educator told us to not switch indiscriminately because it might make a difference. Is there a difference in action between Humalog and NovoLog?

I side with your Certified Diabetes Educator. Both Humalog and NovoLog are analogs of rapid acting insulin and peak sooner than Regular insulin, plus they do not last quite as long. However, NovoLog., at least theoretically, is a bit slower peaking than Humalog and also a bit longer lasting. Some also believe that NovoLog has a different buffer and therefore less precipitation in an insulin pump, but this is not so clearly seen.

In any case, as with any diabetes issue, the proof is what you see with blood glucose control. I would agree that there should not be substitution and that insulin prescriptions should be written to dispense the brand name only so that such problems are not encountered.

SB