What is the onset, peak, and duration of regular (short-acting) insulin?

Regular insulin (Humulin R, Novolin R) is the short-acting insulin. Approximate pharmacokinetics: onset 30-60 minutes, peak 2-4 hours, duration 5-8 hours. Give 30 minutes before meals. The only insulin that can be given IV (for DKA, hyperkalemia, perioperative use). Other insulin types: Rapid-acting (lispro, aspart, glulisine): onset 10-15 min, peak 1-2 hr, duration 3-5 hr — give within 15 min of eating. Intermediate-acting (NPH/Humulin N): onset 1-2 hr, peak 4-12 hr, duration 14-24 hr — cloudy appearance, mix gently before drawing up. Long-acting (glargine/Lantus, detemir/Levemir): onset 1-2 hr, no pronounced peak, duration 24 hr — never mix with other insulins, give once daily. Ultra-long acting (degludec/Tresiba): duration >40 hr. NCLEX commonly tests insulin onset/peak/duration because peak times are when hypoglycemia risk is highest, and timing relative to meals is critical for blood sugar control.