What is the recommended insulin regimen and mixing guidelines for a patient with diabetes requiring insulin therapy?

Insulin Types and Mixing Guidelines

Available Insulin Types

Rapid-Acting Insulin Analogs

• Lispro, aspart, and glulisine have an onset of action within 0-15 minutes and should be administered immediately before meals 1, 2
• A newer faster-acting formulation of insulin aspart was FDA-approved in September 2017 1
• These insulins are preferred for mealtime bolus dosing due to their prompt onset of action 1

Short-Acting Insulin

• Regular insulin is clear in appearance and can be mixed with intermediate-acting insulins 1
• Has a slower onset than rapid-acting analogs but longer duration of action 1

Intermediate-Acting Insulin

• NPH insulin is uniformly cloudy and can be mixed with rapid-acting or short-acting insulins 1
• When mixed with rapid-acting insulin, there is a slight decrease in absorption rate but not total bioavailability 1

Long-Acting Basal Insulin Analogs

• Insulin glargine (Lantus) is clear and colorless, administered once daily at the same time each day 3
• Insulin detemir is another long-acting option 1
• Insulin degludec (U-200) is available in concentrated formulation 1
• These provide steady basal insulin coverage without pronounced peaks 1, 4

Premixed Insulin Products

• NPH/Regular 70/30 contains 70% NPH insulin and 30% regular insulin 1
• Premixed insulin therapy (human insulin 70/30) has been associated with unacceptably high rates of iatrogenic hypoglycemia and is not recommended in the hospital 1

Concentrated Insulin Preparations

• U-500 regular insulin is five times as concentrated as U-100, with delayed onset and longer duration possessing both prandial and basal properties 1
• U-300 glargine has a longer duration of action than U-100 glargine 1
• U-200 degludec and U-200 lispro are available for patients requiring large doses 1

Critical Mixing Guidelines

Insulins That Can Be Mixed

• Rapid-acting insulin can be mixed with NPH, lente, and ultralente 1
• When rapid-acting insulin is mixed with intermediate- or long-acting insulin, inject within 15 minutes before a meal 1
• Currently available NPH and short-acting insulin formulations when mixed may be used immediately or stored for future use 1

Insulins That Should NOT Be Mixed

• Insulin glargine should not be mixed with other forms of insulin due to the low pH of its diluent 1, 3
• Do not dilute or mix Insulin Glargine with any other insulin or solution 3
• Mixing of short-acting and lente insulins is not recommended except for patients already adequately controlled on such a mixture, as Zn²⁺ present in lente insulins will bind with short-acting insulin and delay its onset 1
• Phosphate-buffered insulins (e.g., NPH) should not be mixed with lente insulins as zinc phosphate may precipitate 1

Special Mixing Considerations

• No other medication or diluent should be mixed with any insulin product unless approved by the prescribing physician 1
• When rapid-acting and NPH are mixed, there is no blunting of the onset of action of the rapid-acting insulin 1
• Patients who are well controlled on a particular mixed-insulin regimen should maintain their standard procedure for preparing insulin doses 1

Visual Inspection Guidelines

• Rapid- and short-acting insulins as well as insulin glargine should be clear 1, 3
• All other insulin types should be uniformly cloudy 1
• Only use if the solution is clear and colorless with no visible particles for insulin glargine 3
• Visually inspect vials and pens for particulate matter and discoloration prior to administration 3

Administration Guidelines

Injection Sites and Rotation

• Administer subcutaneously into the abdominal area, thigh, or deltoid 3
• Rotate injection sites within the same region from one injection to the next to reduce the risk of lipodystrophy and localized cutaneous amyloidosis 3
• Do not inject into areas of lipodystrophy or localized cutaneous amyloidosis as repeated injections into these areas result in hyperglycemia 3
• A sudden change in injection site to an unaffected area has been reported to result in hypoglycemia 3

Routes to Avoid

• Do not administer intravenously or via an insulin pump for insulin glargine 3
• Intramuscular (IM) injections should be avoided, especially with long-acting insulins, because severe hypoglycemia may result 2

Needle Safety

• The shortest needles (4-mm pen and 6-mm syringe needles) are safe, effective, and less painful and should be the first-line choice in all patient categories 2
• Insulin Glargine SoloStar prefilled pens must never be shared between patients, even if the needle is changed 3
• Patients using vials must never re-use or share needles or syringes with another person 3

Storage and Handling

• Always check insulin labels before administration 3
• The person with diabetes should always try to relate any unexplained increase in blood glucose to possible reductions in insulin potency 1
• If uncertain about the potency of a vial of insulin, replace the vial in question with another of the same type 1