Before you start using Humulin N insulin, talk to your doctor about your health history and the medicines you're taking. People with other health problems or those taking different diabetes medicines like Actos or Avandia may need to change their Humulin N dose or try a different insulin. If you have kidney issues, liver issues, or heart problems, using Humulin N might be riskier for you. It's important to discuss all of this with your doctor before using it.