What type of insulin is Novolin N (NPH insulin)?

Novolin N Classification

Novolin N is an intermediate-acting NPH (Neutral Protamine Hagedorn) insulin used as basal insulin therapy. 1

Insulin Type and Pharmacokinetics

• NPH insulin is classified as an intermediate-acting insulin, distinct from rapid-acting, short-acting, and long-acting formulations 1

• The onset of action begins approximately 1-2 hours after subcutaneous injection, with peak effect occurring 4-6 hours post-injection 2, 3

• The duration of action extends up to 24 hours, though the primary glucose-lowering effect diminishes significantly after 12-16 hours 4, 3

• NPH contains protamine and zinc as stabilizing agents, which create the cloudy suspension appearance and intermediate-acting profile 4

Role as Basal Insulin

• NPH functions as basal insulin to restrain hepatic glucose production and control hyperglycemia overnight and between meals 5

• The American Diabetes Association categorizes NPH alongside long-acting insulin analogs (glargine, detemir, degludec) and continuous pump delivery as basal insulin options 5

• However, NPH has important limitations compared to modern long-acting analogs, including a more pronounced peak effect rather than the flat, peakless profile of newer basal insulins 5, 2

Clinical Characteristics

• NPH must be mixed before each injection because the insulin suspension settles at the bottom of the vial or cartridge 4

• Visual inspection should reveal a uniformly cloudy or milky appearance after mixing—clear liquid indicates loss of potency 1, 4

• NPH can be mixed with rapid-acting or short-acting insulins in the same syringe, unlike insulin glargine which cannot be mixed due to its acidic pH 1

Comparison to Long-Acting Analogs

• Long-acting basal insulin analogs demonstrate superiority over NPH with flatter plasma concentration profiles, reduced symptomatic and nocturnal hypoglycemia risk, and more predictable glycemic control 5

• The primary advantage of NPH is significantly lower cost compared to long-acting analogs, making it a viable option for cost-conscious patients 5

• NPH is specifically recommended for steroid-induced hyperglycemia because its 4-6 hour peak aligns with the peak hyperglycemic effect of morning glucocorticoid administration 5, 6, 7

Storage and Handling

• Unopened vials should be refrigerated at 36-46°F (2-8°C) but never frozen 1, 4

• In-use vials may be kept at room temperature below 86°F (30°C) to reduce injection site discomfort from cold insulin 1, 4

• Unrefrigerated cartridges must be discarded after 10 days, even if insulin remains 4