Insulin Therapy Guidelines

Insulin Mixing and Administration

The American Diabetes Association recommends that NPH can be mixed with rapid-acting or short-acting insulins, and should be injected within 15 minutes before a meal when mixed with rapid-acting insulin 1
NPH should not be mixed with phosphate-buffered insulins or lente insulins due to potential precipitation and unpredictable action, as advised by the American Diabetes Association 1
The pharmacokinetic profile of rapid-acting insulin is slightly affected when mixed with NPH, with a small decrease in absorption rate but not total bioavailability, according to the American Diabetes Association 1

The initial dose of basal insulin can be 10 units per day or 0.1-0.2 units/kg per day, with titration based on fasting glucose values, as suggested by the American Diabetes Association 2, 3, 4
Using excessive doses of NPH (>0.5 IU/kg) may lead to overbasalization, causing high bedtime-morning glucose differentials and increased hypoglycemia risk, as reported by the American Diabetes Association 5
Basal insulin doses may need to be increased by 20-30% from baseline during steroid therapy, according to the American College of Endocrinology 6, 7
When tapering steroids, insulin must be reduced proportionally to prevent hypoglycemia, considering a ratio of approximately 0.4-0.5 units of NPH per mg of prednisone, as recommended by the American College of Endocrinology 8, 3, 6, 7

The target blood glucose range should be 140-180 mg/dL for most hospitalized patients, and 80-180 mg/dL for patients with specific conditions, with titration of NPH dose by 10-20% every 1-2 days based on glucose patterns 7, 6, 9
Blood glucose should be checked 4 times daily (before meals and at bedtime), with particular attention in the afternoon and evening when prednisone effect peaks, and all patients should receive education about glucose monitoring, symptoms of severe hyperglycemia, and when to seek medical attention 10
Monitoring for hypoglycemia is necessary, especially in diabetic patients during adrenal crisis, with a recommended target blood glucose range of 80-180 mg/dL 11, 12, 13, 8, 14, 15

In patients with heart failure and diabetes, careful consideration of medication choices is necessary, with metformin and SGLT-2 inhibitors as preferred agents when adequate glycemic control can be achieved without insulin, as recommended by the American Heart Association 16
For COVID-19 patients with diabetes, corticosteroids are strongly recommended only for those with severe or critical disease requiring oxygen therapy or mechanical ventilation, with strict glycemic monitoring and control, as supported by the World Health Organization (WHO) guidelines 17
The diagnosis of steroid-induced diabetes is established with two abnormal tests:

Test	Threshold
Random glucose	≥11.1 mmol/L
HbA1c	≥6.5%

Consider simplifying insulin regimens in older adults by changing the timing of basal insulin from bedtime to morning, discontinuing prandial insulin if doses are ≤10 units, and adding non-insulin agents, according to the American Diabetes Association 4
Reduce basal insulin by 25% the evening before surgery to achieve better perioperative glucose control with lower hypoglycemia risk, as advised by the American Diabetes Association 13

NPH insulin should be stored according to manufacturer guidelines, typically refrigerated when not in use, as recommended by the American Diabetes Association 1
Visual inspection before use is important: NPH insulin should appear uniformly cloudy; any clumping, frosting, precipitation, or change in clarity may indicate loss of potency, as advised by the American Diabetes Association 1
The peak effect of NPH insulin occurs at approximately 8-12 hours after injection, according to the American Diabetes Association 18