How should I write an order for a regular insulin IV infusion (e.g., 100 U in 100 mL normal saline) in an adult ICU patient with severe hyperglycemia (blood glucose ≥250 mg/dL) or diabetic ketoacidosis?

How to Order an Insulin Drip for Severe Hyperglycemia or DKA in the ICU

Prepare 100 units of regular human insulin in 100 mL of 0.9% normal saline (concentration: 1 U/mL), prime the tubing with 20 mL, and initiate at 0.1 U/kg/hour after confirming serum potassium ≥3.3 mEq/L. 1

Absolute Prerequisite: Check Potassium First

Do not start insulin if serum potassium is <3.3 mEq/L—this is an absolute contraindication. 1 Insulin drives potassium intracellularly and can precipitate life-threatening arrhythmias in hypokalemic patients. 1

• If K⁺ <3.3 mEq/L: Hold insulin, give aggressive IV potassium replacement, and recheck levels before starting insulin 1
• If K⁺ 3.3–5.5 mEq/L: Safe to start insulin; add 20–30 mEq/L potassium to IV fluids once urine output is adequate 1
• If K⁺ >5.5 mEq/L: Start insulin immediately but delay potassium supplementation until level falls below 5.5 mEq/L 1

Standard Insulin Drip Order

Preparation

• Solution: Add 100 units regular human insulin to 100 mL 0.9% sodium chloride (final concentration 1 U/mL) 2, 1
• Priming: Flush tubing with 20 mL of the prepared solution before connecting to patient to prevent insulin adsorption and ensure accurate delivery 2, 1

Initial Dosing for DKA

For moderate-to-severe DKA:

• Give IV bolus: 0.1 U/kg regular insulin as direct push 1
• Start continuous infusion: 0.1 U/kg/hour 1
• Target glucose decline: 50–75 mg/dL per hour 1

For pediatric patients or mild DKA:

• Omit the bolus 1, 3
• Start continuous infusion at 0.05–0.1 U/kg/hour 1
• This reduces cerebral edema risk in children 1

Initial Dosing for Non-DKA ICU Hyperglycemia

• Start at 0.5–1 U/hour 1
• Target glucose: 140–180 mg/dL 2, 1

Concurrent Fluid Management

First Hour

• Isotonic saline (0.9% NaCl) at 15–20 mL/kg/hour 1

When Glucose Falls to 250 mg/dL

Critical step: Switch IV fluid to 5% dextrose with 0.45–0.75% NaCl while maintaining the same insulin infusion rate 1, 4

This is essential because ketone clearance takes longer than glucose correction—never stop insulin just because glucose normalizes. 4 The goal is to maintain glucose 150–200 mg/dL until full DKA resolution. 1, 4

For Euglycemic DKA (glucose <250 mg/dL at presentation)

• Start D5W with normal saline from the beginning of insulin therapy 1

Potassium Replacement Protocol

• Add 20–30 mEq/L potassium to each liter of IV fluid once K⁺ <5.5 mEq/L and urine output adequate 1
• Use mixture of 2/3 potassium chloride (or acetate) and 1/3 potassium phosphate 1
• Target serum potassium: 4.0–5.0 mEq/L throughout treatment 1
• Monitor potassium every 2–4 hours 1

Monitoring Requirements

Glucose

• Every 1–2 hours during initial titration 1
• Every 2–4 hours once stable 1

Electrolytes & Metabolic Parameters (for DKA)

• Every 2–4 hours: potassium, sodium, chloride, bicarbonate, anion gap, BUN, creatinine, venous pH, osmolality 1, 4
• Venous pH is sufficient—no need for repeat arterial blood gases 4

Titration Algorithm

If glucose not falling by 50 mg/dL in first hour:

1. Verify adequate hydration 1
2. Double insulin infusion rate every hour until achieving 50–75 mg/dL/hour decline 1

For severe, refractory DKA:

• May require 4–6 U/hour or higher with concurrent 10–20% dextrose infusion to prevent hypoglycemia while clearing ketones 5
• Continue high-dose insulin until serum bicarbonate normalizes, which may take several days in severe cases 5

DKA Resolution Criteria

All of the following must be met: 4

• Glucose <200 mg/dL
• Serum bicarbonate ≥18 mEq/L
• Venous pH >7.3
• Anion gap ≤12 mEq/L

Transition to Subcutaneous Insulin

This is the most common error leading to DKA recurrence—follow this sequence exactly:

1. Administer long-acting basal insulin (glargine or detemir) subcutaneously 2–4 hours before stopping IV insulin 1
2. Continue IV insulin infusion for 1–2 hours after the basal dose 1
3. Basal dose = approximately 50% of total 24-hour IV insulin amount 1
4. Divide remaining 50% equally among three meals as rapid-acting prandial insulin 1

Never stop IV insulin abruptly without this overlap—it is the leading cause of recurrent DKA. 1

Alternative Approach for Mild-Moderate Uncomplicated DKA

For hemodynamically stable, alert patients with mild-moderate DKA, subcutaneous rapid-acting insulin analogs (0.1–0.2 U/kg every 1–2 hours) combined with aggressive IV fluids can be as effective and more cost-effective than IV insulin. 1, 6 This requires:

• Hemodynamic stability 6
• Alert mental status 6
• Frequent bedside glucose monitoring 1
• Non-ICU setting acceptable 6

Common Pitfalls to Avoid

1. Starting insulin with K⁺ <3.3 mEq/L → life-threatening arrhythmias 1
2. Stopping insulin when glucose normalizes → persistent ketoacidosis; instead add dextrose and continue insulin 4
3. Discontinuing IV insulin without 2–4 hour basal insulin overlap → DKA recurrence 1
4. Using rapid-acting insulin analogs IV → only regular insulin is approved for IV use 1
5. Inadequate potassium monitoring → severe hypokalemia as insulin drives K⁺ intracellularly 1

When IV Insulin is Preferred Over Subcutaneous

• Hemodynamically unstable patients requiring vasopressors 2
• Type 1 diabetes in ICU 2
• Severe DKA (pH <7.0, bicarbonate <10 mEq/L) 1
• Need for rapid, flexible titration 2
• Peripheral edema present 2
• Frequent interruptions of nutrition anticipated 2