What do all NPH insulins contain?

NPH insulin is classified as an intermediate-acting insulin and is distinct from other types of insulins due to its specific formulation. The key component that differentiates NPH (Neutral Protamine Hagedorn) insulin is the presence of protamine; this is what the "N" stands for in its name. Protamine is a protein that prolongs the action of insulin by forming a stable complex with the insulin, which slows down its absorption and action. Therefore, all NPH insulins contain the "N" in their designation, indicating the presence of protamine and their specific pharmacological properties. This classification helps healthcare providers identify the insulin’s duration of action and the appropriate contexts for its use.