How to manage severe hyperglycemia in a patient with type 2 diabetes mellitus (T2DM) and a random blood sugar (RBS) level of 490 mg/dl, using intravenous (IV) insulin infusion?

Management of Severe Hyperglycemia with IV Insulin Infusion in Type 2 Diabetes

For a 150 kg patient with type 2 diabetes and random blood glucose of 490 mg/dL, initiate continuous intravenous insulin infusion immediately, as this represents a hyperglycemic crisis requiring urgent intervention to prevent morbidity and mortality. 1

Initial Assessment and Diagnosis

Before starting IV insulin, you must determine whether this is diabetic ketoacidosis (DKA), hyperosmolar hyperglycemic state (HHS), or uncomplicated severe hyperglycemia 1:

• Obtain immediately: venous blood gas, serum electrolytes (especially potassium), blood urea nitrogen, creatinine, osmolality, and urinalysis to check for ketones 1
• DKA criteria: blood glucose >250 mg/dL, venous pH <7.3, bicarbonate <15 mEq/L, and moderate ketonuria or ketonemia 1
• HHS criteria: blood glucose >600 mg/dL, venous pH >7.3, bicarbonate >15 mEq/L, with altered mental status or severe dehydration 1

This patient's glucose of 490 mg/dL suggests either mild DKA, early HHS, or severe hyperglycemia without ketoacidosis—the lab results will guide your specific protocol 1.

IV Insulin Infusion Protocol

Start continuous IV regular insulin infusion at 0.1 units/kg/hour, which equals 15 units/hour for this 150 kg patient. 1

Insulin Dosing Details:

• No initial bolus is necessary for most cases of severe hyperglycemia in type 2 diabetes, though some protocols use 0.1 units/kg IV bolus before starting the infusion 1
• Target glucose decline: 50-75 mg/dL per hour 2, 3
• Monitor blood glucose every 1-2 hours initially, then every 2-4 hours once stable 1

Adjusting the Infusion Rate:

• If glucose is not declining by at least 50 mg/dL in the first hour, double the insulin infusion rate 3
• Once glucose reaches 250 mg/dL, reduce insulin infusion rate to 0.05 units/kg/hour (7.5 units/hour for this patient) and add dextrose 5% to IV fluids 1
• Never stop the insulin infusion abruptly—maintain at least 0.5-1 unit/hour until transition to subcutaneous insulin is complete 1

Concurrent Fluid Resuscitation

Aggressive fluid replacement is equally critical and must be initiated simultaneously with insulin 1:

• Start with 0.9% normal saline at 15-20 mL/kg/hour (approximately 2-3 liters in the first hour for this patient) if hemodynamically unstable 1
• After initial resuscitation, continue at 250-500 mL/hour, adjusting based on hydration status, electrolytes, and urine output 1
• Switch to 0.45% saline if corrected serum sodium is elevated 1

Potassium Management—Critical Pitfall

This is where most errors occur—insulin drives potassium intracellularly and can cause life-threatening hypokalemia 1:

• **Do NOT start insulin if serum potassium is <3.3 mEq/L**—give potassium replacement first until >3.3 mEq/L 1
• If potassium is 3.3-5.2 mEq/L, add 20-30 mEq potassium to each liter of IV fluid (use 2/3 KCl and 1/3 KPO4) 1
• If potassium is >5.2 mEq/L, do not add potassium initially but recheck in 2 hours 1
• Monitor potassium every 2-4 hours during insulin infusion 1

Monitoring During IV Insulin Therapy

Check the following every 2-4 hours 1:

• Blood glucose (more frequently in first few hours)
• Serum electrolytes (sodium, potassium, chloride, bicarbonate)
• Anion gap (if DKA suspected)
• Venous pH (if DKA)
• Blood urea nitrogen and creatinine

Transition to Subcutaneous Insulin

Plan the transition carefully to avoid rebound hyperglycemia—this is a common pitfall 1:

Timing of Transition:

• For DKA: when glucose <200 mg/dL, bicarbonate ≥18 mEq/L, and venous pH >7.3 1
• For HHS or severe hyperglycemia: when glucose <250 mg/dL and patient is clinically stable 1

Calculating Subcutaneous Insulin Dose:

Use the total IV insulin given in the last 24 hours to calculate subcutaneous requirements 1:

• Total daily dose (TDD) = 50% of the 24-hour IV insulin total 1
• Give 50% as basal insulin (long-acting: glargine or detemir) once daily 1
• Give remaining 50% as prandial insulin (rapid-acting: lispro, aspart, or glulisine) divided before three meals 1

Example for this patient: If IV insulin totaled 360 units in 24 hours:

• TDD subcutaneous = 180 units
• Basal insulin = 90 units once daily
• Prandial insulin = 30 units before each meal 1

Critical Overlap Period:

Continue IV insulin for 1-2 hours AFTER giving the first subcutaneous basal insulin dose 1. This overlap prevents a gap in insulin coverage that leads to rebound hyperglycemia—a very common error 1.

Special Considerations for This 150 kg Patient

Given the severe obesity (150 kg), consider these factors:

• Higher insulin resistance is expected—may require higher infusion rates (up to 0.15-0.2 units/kg/hour) if glucose doesn't decline adequately 3
• Screen for HHS rather than DKA, as type 2 diabetes patients with severe hyperglycemia more commonly develop hyperosmolar state 1
• Calculate osmolality: 2(Na) + glucose/18 + BUN/2.8; if >320 mOsm/L, this is HHS requiring ICU-level care 1

When to Avoid or Modify This Approach

Do not use IV insulin infusion for mild hyperglycemia—subcutaneous insulin is equally effective and safer for glucose <300 mg/dL without acidosis or altered mental status 1, 4, 5.

Consider short-term intensive insulin therapy (STII) as an alternative strategy: For newly diagnosed type 2 diabetes with severe hyperglycemia, 2 weeks of intensive subcutaneous insulin (basal-bolus regimen at 0.3-0.4 units/kg/day) can restore beta-cell function and achieve remission rates of 45-51% at 1 year 4. However, this patient's acute presentation with RBS 490 mg/dL requires immediate IV therapy first 1, 6.

Post-Crisis Long-Term Management

Once stabilized on subcutaneous insulin 6:

• Continue metformin if no contraindications (eGFR >30 mL/min) 6
• Target fasting glucose 100-120 mg/dL and postprandial <180 mg/dL 6
• Provide glucagon prescription and hypoglycemia education 6
• Follow up within 2-4 weeks to adjust insulin doses based on home glucose monitoring 6