Final answer:
The potential side effect of Insulin Isophane Suspension NPH (Humulin N, Novolin N) is hypoglycemia, or low blood glucose levels.
Step-by-step explanation:
The potential side effect of Insulin Isophane Suspension NPH (Humulin N, Novolin N) is Hypoglycemia, which is low blood glucose levels. When insulin is injected, it allows for the transport and storage of glucose, decreasing blood glucose levels. If the dose of insulin is excessive, it can result in severe and persistent hypoglycemia, indicating that the insulin dose needs to be reduced.