How is hyponatremia (low sodium levels) due to hyperglycemia (high blood glucose) treated?

Treatment of Hyperglycemia-Induced Hyponatremia

The primary treatment is insulin therapy to lower blood glucose, which will automatically correct the pseudohyponatremia, while simultaneously correcting the measured sodium for hyperglycemia to guide fluid management. 1

Understanding the Mechanism

Hyperglycemia causes a dilutional hyponatremia through osmotic water shift from intracellular to extracellular compartments. 2 This is not true hyponatremia requiring sodium replacement—it's a mathematical artifact that resolves when glucose normalizes.

Corrected Sodium Calculation

For every 100 mg/dL glucose above 100 mg/dL, add 1.6 mEq/L to the measured sodium value to obtain the corrected serum sodium. 2, 1 This corrected value guides your actual fluid management decisions, not the measured sodium.

Treatment Algorithm

Step 1: Assess Severity and Exclude Hypokalemia

• Check potassium first—if K+ <3.3 mEq/L, hold insulin and replace potassium before starting insulin therapy. 2, 1
• Determine if patient has DKA (pH <7.3, ketones present) or HHS (pH ≥7.3, glucose typically >600 mg/dL, effective osmolality >320 mOsm/kg). 2

Step 2: Initiate Insulin Therapy

For adults with DKA or HHS, administer IV bolus of regular insulin at 0.15 units/kg body weight, followed by continuous infusion at 0.1 unit/kg/hour (5-7 units/hour). 2, 1

• Target glucose decline of 50-75 mg/dL/hour. 2, 1
• If glucose doesn't fall by 50 mg/dL in the first hour, double the insulin infusion rate hourly until achieving steady decline. 2
• When glucose reaches 250 mg/dL (DKA) or 300 mg/dL (HHS), decrease insulin to 0.05-0.1 units/kg/hour and add dextrose 5-10% to IV fluids. 2

Step 3: Fluid Management Based on Corrected Sodium

Initial fluid resuscitation with 0.9% NaCl (isotonic saline) at 10-20 mL/kg/hour for the first hour in adults. 2, 1

After initial resuscitation, fluid choice depends on corrected sodium:

• If corrected sodium is low: continue 0.9% NaCl at 4-14 mL/kg/hour 2
• If corrected sodium is normal or elevated: switch to 0.45% NaCl at 4-14 mL/kg/hour 2

Step 4: Potassium Replacement

Once renal function is confirmed and K+ is known, add 20-30 mEq/L potassium (2/3 KCl and 1/3 KPO4) to IV fluids. 2, 1 Insulin drives potassium intracellularly, and hypokalemia during treatment is a critical complication to prevent. 1, 3

Critical Pitfalls to Avoid

Do Not Treat the Measured Sodium Directly

The measured hyponatremia will automatically correct as glucose normalizes—attempting to correct it with hypertonic saline or excessive sodium administration can cause dangerous hypernatremia. 4, 5 One case report documented corrected sodium rising to >190 mEq/L when this principle was ignored. 4

Monitor Osmolality Changes Carefully

The induced change in serum osmolality should not exceed 3 mOsm/kg/H2O per hour. 2 Rapid osmolality shifts—whether from hypo- to hypernatremia or vice versa—can cause osmotic demyelination syndrome (central pontine myelinolysis). 6

Pediatric Considerations

For patients <20 years old:

• Initial reexpansion should not exceed 50 mL/kg over first 4 hours 2
• Continue fluid therapy at 1.5 times 24-hour maintenance requirements 2, 1
• No initial insulin bolus—start continuous infusion only 2
• Risk of cerebral edema is significantly higher in pediatric patients with rapid fluid administration. 2

Monitoring During Treatment

• Measure glucose hourly until stable decline achieved 2
• Check electrolytes (including corrected sodium) every 2-4 hours 2
• Monitor mental status continuously—failure to improve despite glucose normalization may indicate the corrected sodium was severely elevated and requires specific attention to free water deficit. 4
• Assess for signs of fluid overload or cerebral edema, particularly in pediatric patients 2

Special Circumstance: Extreme Hyperglycemia with True Hypernatremia

In rare cases where corrected sodium is severely elevated (>190 mEq/L), consider:

• Dextrose 5% in water (D5W) plus Ringer's lactate 4
• Free water administration via nasogastric tube 4
• IV desmopressin to improve free water deficit 4

This scenario represents true hypernatremia coexisting with hyperglycemia and requires aggressive free water replacement beyond standard protocols. 4