Hi @Susan SS, Welcome to the forum.
Humulin insulins are based on regular human insulin. I think Humulin I is called NPH outside the UK. NPH is a 'cloudy' insulin with added zinc to give it a longer profile than regular human insulin, it is slower to start and longer to finish working.
It is 'peaky' and tends to have its peak action at 4-8 hours,and last 10-12 hours. Where as Levemir is supposed not to peak over its duration.
Often NPH is used to offer some meal coverage, as well as covering basal, and taken 2-3 times a day.
When changing from Levemir to NPH you will need to adjust the dosage and timing to suit the new profile.
