Insulin Therapy

Types of Insulin

• Human insulin is available in rapid-acting, short-acting, intermediate-acting, and long-acting types that can be injected separately or mixed in the same syringe to optimize glycemic control, according to the American Diabetes Association 1, 2
• Long-acting insulins, such as insulin glargine, provide basal insulin coverage with less risk of hypoglycemia, and have a duration of 20-42+ hours 1, 2
• The following table summarizes the pharmacokinetic properties of different insulin types:

3

• Insulin glargine should not be mixed with other insulins due to its acidic pH, as recommended by the American Diabetes Association 1, 2

Insulin Storage and Handling

• Unopened insulin vials should be refrigerated, and opened vials should be discarded after 28 days, even if insulin remains, to prevent loss of potency, according to the American Diabetes Association 1
• Insulin potency may decrease after the bottle has been in use for more than one month, especially if stored at room temperature, as reported by the American Diabetes Association 1, 2

Insulin Regimens

• The American Diabetes Association recommends a basal-bolus regimen that includes carbohydrate counting to match mealtime insulin, regular blood glucose monitoring, and insulin dose adjustments based on glycemic patterns to optimize control and reduce complications 4
• Commercially available premixed insulins may be used if the ratio is appropriate for the patient's needs, according to the American Diabetes Association 1
• When mixing rapid-acting insulin with intermediate or long-acting insulin, it is recommended to inject within 15 minutes before a meal, as suggested by the American Diabetes Association 1

Blood Glucose Monitoring

• The American Diabetes Association suggests minimum 4 times daily monitoring, with additional checks 2 hours after meals to assess postprandial control and during suspected hypoglycemia, and periodic 2-3 AM checks to assess for nocturnal hypoglycemia 3
• Continuous glucose monitoring (CGM) can provide more comprehensive data if available 3
• Blood glucose should be monitored regularly, with four or more tests per day generally necessary for optimal control, and HbA1c should be measured every 3 months to assess overall glycemic control, with a target HbA1c of <7.0% (individualized based on hypoglycemia risk) 5, 6, 4

Insulin Dose Adjustments

• The American Diabetes Association recommends adjusting insulin doses based on glycemic patterns, with a target fasting glucose of 80-130 mg/dL 4
• If fasting glucose consistently >130 mg/dL for 3 days, increase basal insulin by 2 units, and if fasting glucose consistently <80 mg/dL or nocturnal hypoglycemia occurs, decrease by 2 units, with a maximum adjustment of 10-20% of current dose at one time 4
• Basal insulin can be started at a dose of 0.1-0.2 units/kg/day, and titrated by increasing by 10-15% or 2-4 units once or twice weekly until target fasting glucose is achieved, as recommended by the American College of Physicians 7
• Mealtime insulin can be started at a dose of 4 units per meal or 10% of the basal dose, according to the American College of Physicians 7

Carbohydrate Counting and Insulin-to-Carbohydrate Ratio

• The American Diabetes Association recommends teaching patients to count carbohydrates and calculate pre-meal doses, with a starting insulin-to-carbohydrate ratio (ICR) of 1 unit per 15g carbohydrate (adjust based on response) 8
• The American Diabetes Association recommends beginning with one injection before the meal with the largest glucose excursion (typically dinner), then adding a second injection before breakfast if needed, and finally adding a third injection before lunch if glycemic targets are not met 9

Hypoglycemia Management

• The American Diabetes Association recommends treating mild/moderate hypoglycemia (<70 mg/dL) with 15g fast-acting carbohydrate, rechecking in 15 minutes, and repeating treatment if still <70 mg/dL, followed by a small protein-containing snack if next meal is >1 hour away 8
• For patients experiencing frequent hypoglycemia, consider reducing the total basal insulin dose by 10-20%, switching to a longer-acting analog with less peak effect (e.g., degludec), or evaluating for overbasalization, as recommended by the American Diabetes Association 10, 3

Special Populations

• Elderly patients may require lower doses and more frequent monitoring to reduce hypoglycemia risk, as recommended by the Diabetes Care guidelines 11
• Patients with pre-meal hyperglycemia (>180 mg/dL) may benefit from injecting rapid-acting insulin 15 minutes before meals for better postprandial control, as recommended by the American Diabetes Association 12
• For patients requiring large insulin doses, U-200 lispro (200 units/mL) is available for patients needing higher doses with less injection volume 13
• Higher concentration insulins, such as U-500 Regular, U-300 Glargine, and U-200 Degludec, are indicated for patients requiring large insulin doses (>200 units/day) and reduce injection volume for large doses, but are contraindicated in patients with chronic lung disease and not recommended for smokers, as stated by the American College of Physicians 7
• The American Diabetes Association suggests reducing pre-meal Admelog by 25-50% for the meal before planned exercise, and considering additional carbohydrate intake (15-30g per hour of moderate activity) for prolonged activity, with monitoring for delayed hypoglycemia up to 24 hours after significant activity 8