What treatment should be given to a patient with severe hyperglycemia (blood glucose level > 300 mg/dL)?

Management of Severe Hyperglycemia (Blood Glucose >300 mg/dL)

For a patient with blood glucose >300 mg/dL, immediately initiate intravenous insulin therapy with continuous infusion after assessing for diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS), as this represents a metabolic emergency requiring aggressive treatment to prevent morbidity and mortality. 1

Immediate Assessment

Before initiating treatment, rapidly evaluate the following to determine the severity and guide management:

• Check for ketosis: Measure blood or urine ketones in all patients with type 1 diabetes and insulin-treated type 2 diabetes 2, 1
• Assess hydration status: Severe dehydration is common and requires immediate correction 3
• Obtain venous blood gas, electrolytes (especially potassium), BUN, creatinine, and calculate anion gap to identify DKA or HHS 1
• Evaluate mental status: Altered consciousness suggests HHS or severe DKA requiring ICU-level care 3

Treatment Protocol

For Patients with DKA or HHS (Ketones Present or Hyperosmolar)

Intravenous insulin is mandatory and should never be delayed: 1

• Priming dose: 0.1 units/kg body weight as IV bolus 1
• Continuous infusion: 0.1 units/kg/hour 1
• Target glucose reduction: 50-75 mg/dL per hour 1
• Monitor blood glucose every 1-2 hours until stable 1

Aggressive fluid resuscitation is critical: 1, 3

• Initial rate: 15-20 mL/kg/hour of isotonic saline (0.9% NaCl) for the first hour 1
• Average requirement: 9 liters over 48 hours in adults 3
• Adjust based on hemodynamic status and avoid volume overload 1

Potassium replacement must begin early: 1

• Start when serum potassium <5.2 mEq/L to prevent life-threatening hypokalemia from insulin therapy 1
• Use 1/3 KPO₄ and 2/3 KCl or K-acetate in replacement solutions 1

For Non-Critically Ill Patients Without Ketosis

If the patient is well-hydrated, ketone-negative, and clinically stable, a basal-bolus subcutaneous insulin regimen may be appropriate: 2

• Basal insulin: Start at 0.3 U/kg/day (reduce home dose by 20% if previously on insulin) 2
• Give half as basal insulin, half as bolus insulin divided before meals 2
• Add correction doses with rapid-acting insulin before meals or every 6 hours 2

However, if blood glucose remains >300 mg/dL despite initial subcutaneous insulin or the patient shows any signs of metabolic decompensation, immediately switch to IV insulin infusion. 2

Critical Monitoring Parameters

Continue intensive monitoring until metabolic stability is achieved: 1

• Blood glucose: Every 1-2 hours during IV insulin 1
• Electrolytes, pH, anion gap: Every 2-4 hours 1
• Continue IV insulin until: Glucose <200 mg/dL AND normalized pH AND improved metabolic parameters 1

Transition to Subcutaneous Insulin

Do not discontinue IV insulin prematurely—this is a common and dangerous error: 1

• Overlap IV and subcutaneous insulin by 1-2 hours to prevent rebound hyperglycemia 1
• Only transition after metabolic stability: Glucose <200 mg/dL, normalized pH, and resolution of ketosis or hyperosmolarity 1

Common Pitfalls to Avoid

• Never delay insulin therapy while awaiting additional tests—this worsens metabolic derangement and increases mortality risk 1
• Never provide inadequate fluid resuscitation—dehydration correction is as critical as insulin therapy 1, 3
• Never stop IV insulin before achieving metabolic stability—premature discontinuation causes rebound hyperglycemia and ketosis 1
• Never forget to monitor and replace potassium—insulin drives potassium intracellularly, causing life-threatening hypokalemia 1
• In the exercise/cardiac rehabilitation setting specifically: If blood glucose is >300 mg/dL, the patient may only exercise if they feel well, are adequately hydrated, and blood/urine ketones are negative; otherwise, contact the physician immediately 2

Target Blood Glucose During Treatment

• For critically ill patients on IV insulin: Target 140-180 mg/dL (7.8-10.0 mmol/L) 2
• Avoid targets <140 mg/dL as this increases hypoglycemia risk and mortality 2, 4
• During acute management of DKA/HHS: Continue IV insulin until glucose <200 mg/dL, then add dextrose to IV fluids while continuing insulin to clear ketosis 1