What is the insulin of choice and dosage for patients with varying blood glucose levels, including hyperglycemia (above 250 mg/dL), mild hyperglycemia (between 100-200 mg/dL), and severe hyperglycemia (above 400 mg/dL)?

Insulin Selection and Dosing by Blood Glucose Level

Mild Hyperglycemia (100-200 mg/dL)

For patients with mild hyperglycemia, initiate basal insulin (insulin glargine) at 10 units once daily or 0.1-0.2 units/kg body weight, administered at the same time each day. 1

• Continue metformin unless contraindicated, and possibly one additional non-insulin agent when starting basal insulin 1, 2
• Titrate the dose by 2 units every 3 days if fasting glucose is 140-179 mg/dL until reaching target of 80-130 mg/dL 1
• For patients with fasting glucose in this range, a basal-only approach is typically sufficient initially 1

Moderate Hyperglycemia (250 mg/dL range)

Patients with blood glucose levels around 250 mg/dL require aggressive basal insulin titration with 4 units every 3 days, plus immediate addition of prandial insulin coverage. 1

• Start basal insulin at 0.3-0.4 units/kg/day given the marked hyperglycemia 1
• Add prandial insulin immediately with 4 units of rapid-acting insulin before the largest meal, or use 10% of the basal dose 1
• Increase basal insulin by 4 units every 3 days if fasting glucose remains ≥180 mg/dL 1
• Titrate prandial insulin by 1-2 units or 10-15% every 3 days based on 2-hour postprandial glucose readings 1

Severe Hyperglycemia (>400 mg/dL or HbA1c ≥10-12%)

For severe hyperglycemia above 400 mg/dL or HbA1c ≥10-12% with symptomatic or catabolic features, immediately initiate basal-bolus insulin therapy with total daily dose of 0.3-0.5 units/kg/day. 1, 3

• Divide the total daily dose: 50% as basal insulin (glargine) once daily and 50% as prandial insulin divided among three meals 1, 2
• For a 70 kg patient with severe hyperglycemia, this translates to approximately 21-35 units total daily: 10-17 units basal insulin and 3-6 units before each meal 1
• Increase basal insulin by 4 units every 3 days until fasting glucose reaches 80-130 mg/dL 1
• Use rapid-acting insulin analogs (lispro, aspart) 0-15 minutes before meals rather than regular insulin 4, 5

Hospitalized Patients with Hyperglycemia

For non-critically ill hospitalized patients with blood glucose >300 mg/dL, start with 0.3 units/kg/day as total daily dose, giving half as basal insulin and half as bolus insulin divided among meals. 3

• For patients on high-dose home insulin (≥0.6 units/kg/day), reduce the total daily dose by 20% upon hospitalization to prevent hypoglycemia 1, 2
• Use lower doses of 0.1-0.25 units/kg/day for high-risk patients: elderly >65 years, those with renal failure, or poor oral intake 1
• Target glucose range is 140-180 mg/dL for non-critically ill hospitalized patients 3
• Avoid sliding scale insulin as monotherapy—it is explicitly condemned by all major diabetes guidelines and associated with poor outcomes 1, 3

Critical Threshold Monitoring

When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, stop escalating basal insulin and add prandial insulin instead. 1

• Clinical signals of overbasalization include: basal dose >0.5 units/kg/day, bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia, and high glucose variability 1
• Further basal insulin escalation beyond this threshold produces diminishing returns with increased hypoglycemia risk rather than improved glycemic control 1

Hypoglycemia Management

• If blood glucose <70 mg/dL occurs, reduce the corresponding insulin component by 10-20% immediately 1
• For severe hypoglycemia without clear cause, reduce the dose by 20-50% 3
• Daily fasting blood glucose monitoring is essential during titration 1

Common Pitfalls to Avoid

• Never use sliding scale insulin as monotherapy—it treats hyperglycemia reactively after it occurs rather than preventing it, leading to dangerous glucose fluctuations 1, 3
• Never delay insulin initiation in patients not achieving glycemic goals with oral medications, as this prolongs exposure to hyperglycemia and increases complication risk 1
• Never continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia, as this leads to overbasalization with increased hypoglycemia risk and suboptimal control 1
• Never discontinue metformin when starting insulin unless contraindicated, as this leads to higher insulin requirements and more weight gain 1