This question is about a cat, but I feel it is also relevant to pediatrics because it is about diluting Humulin NPH insulin to give an accurate dose. I have been told by the relevant pharmaceutical representative that diluent is unavailable in this country so pediatric doctors here are diluting the insulin in the syringe with saline. To me, this defeats the purpose as I need to get it as simple as possible for the owner. Do you know if I can dilute NPH with saline to make a one-in-ten solution ? If I do, will it keep for any length of time?

You can have a pharmacist dilute the insulin or you (the vet) may do it yourself. If you are prescribing a diluted insulin, the insulin bottle should be properly labeled to show that the insulin was diluted. For the pet’s caretaker, either you or the pharmacist should write down what the strength (U-#) of the original insulin was plus how much undiluted insulin and how much diluent was used to make the new, diluted insulin. The type of diluent should also be listed. As the vet, this information should of course be in your records, but the owner should also have this information in case of emergency.

I think your pharmaceutical representative is incorrect. Insulin should not be diluted with saline as it can cause injection discomfort and may change the action of the insulin. Insulin should only be diluted with the solution provided by the insulin manufacturer. Diluent and empty vials are free from insulin makers, and Lilly definitely makes an NPH diluent.

RP