Whats the diffence between humulin n and novolin (insulin) r?

Different timing: R is usually given about 1/2 hr prior to a meal. No longer the short acting Insulin of choice because others more effective having shorter 1/2 lives. Nph may be combined with short acting Insulin or given alone to provide later coverage. Starts to peak in ~ 4 hrs, though effect will last for several. It peaks which predisposes people to low sugars. Newer insulins replace nph for better control.