What are the different types of insulin available for patients with diabetes?

Types of Insulin Available for Diabetes Management

Insulin is classified into four main categories based on duration of action: rapid-acting analogs, short-acting (regular human insulin), intermediate-acting, and long-acting insulins, with each type serving distinct roles in achieving glycemic control. 1, 2

Rapid-Acting Insulin Analogs

• Insulin lispro, insulin aspart, and insulin glulisine are the three available rapid-acting analogs with onset of action within 0.25-0.5 hours (15 minutes), peak at 1-3 hours, and duration of 3-5 hours 2, 3
• These should be administered immediately before meals (within 15 minutes) due to their rapid pharmacokinetic profile 3
• Faster-acting insulin aspart is a newer formulation with even more rapid absorption characteristics 1
• Concentrated lispro U-200 provides the same rapid action but in half the injection volume, improving adherence for patients requiring large doses 1
• Inhaled insulin is available as a rapid-acting prandial option but is contraindicated in chronic lung disease (asthma, COPD) and requires spirometry monitoring 1

Short-Acting Insulin

• Regular human insulin is classified separately from rapid-acting analogs as "short-acting" insulin with onset at 30 minutes, requiring administration 30 minutes before meals for optimal effect 1, 4, 2
• U-500 regular insulin is five times more concentrated than U-100, has delayed onset and longer duration resembling intermediate-acting insulin, and is indicated for patients requiring more than 200 units daily 1

Intermediate-Acting Insulin

• NPH (Neutral Protamine Hagedorn) insulin has onset at approximately 1 hour, peak at 6-8 hours, and duration of approximately 12 hours 4, 5
• Lente insulin is another intermediate-acting option, though less commonly used 1
• NPH represents a cost-effective alternative at approximately $25-35 per vial compared to long-acting analogs, though it carries modestly higher hypoglycemia risk 1, 4

Long-Acting Basal Insulin Analogs

• Insulin glargine (U-100 and U-300) provides once-daily basal coverage with relatively peakless action 1
• Insulin detemir offers once- or twice-daily dosing with modestly lower hypoglycemia risk than NPH 1
• Insulin degludec (U-100 and U-200) has the longest duration of action among basal insulins 1
• U-300 glargine has longer duration than U-100 glargine but modestly lower efficacy per unit administered 1
• Long-acting analogs demonstrate moderate-quality evidence for reduced severe hypoglycemia compared to NPH (OR 0.65 for glargine, OR 0.37 for detemir in type 2 diabetes) 1

Premixed Insulin Formulations

• 70% NPH/30% regular, 50% NPH/50% regular are human insulin premixed combinations 1, 2
• 75% NPL/25% insulin lispro, 50% NPL/50% insulin lispro are analog premixed formulations 1, 2
• 70% aspart protamine/30% aspart provides analog-based premixed option 1
• These formulations require relatively fixed meal schedules and carbohydrate content due to the predetermined proportions 1

Critical Storage and Handling Requirements

• Unopened vials must be refrigerated at 36-46°F (2-8°C), avoiding freezing or temperatures exceeding 86°F (30°C) 1, 2
• In-use insulin may be kept at room temperature to reduce injection site irritation from cold insulin 1, 2
• Visual inspection before each use is mandatory: rapid-acting, short-acting, and glargine should appear clear, while all other types should be uniformly cloudy 1
• Lumpy, granular precipitate or solid wall deposits indicate the insulin must be discarded 5

Important Clinical Caveats

• Never interchange insulin species or types without prescriber approval and patient notification, as changes in purity, strength, brand, type, or manufacturing method may necessitate dosage adjustments 1, 2, 5
• When comparing human insulin to analogs, cost differences are substantial while hypoglycemia risk differences are modest and glycemic efficacy differences minimal 1
• In real-world settings with conventional treatment targets, NPH versus long-acting analogs showed no increase in hypoglycemia-related emergency visits or hospitalizations 1
• The method of insulin administration (dose, timing, targets) has greater impact on adverse effects than differences among formulations 1