No, Normal Saline Alone is Insufficient to Reduce Hyperglycemia
Normal saline provides essential volume repletion and helps lower glucose through dilution and improved renal perfusion, but insulin therapy is required to effectively reduce hyperglycemia in most clinical scenarios. 1
Why Saline Alone is Inadequate
Limited Glucose-Lowering Effect
Saline infusion produces only modest glucose reductions through hemodilution and enhanced urinary glucose excretion, but does not address the fundamental insulin deficiency or resistance driving hyperglycemia. 2
In the GIST-UK trial, patients receiving saline alone (without insulin) showed spontaneous decline in plasma glucose levels, but maintained significantly higher glucose levels (mean ~122 mg/dL between hours 8-24) compared to those receiving insulin therapy. 1
Research demonstrates that saline infusion in hyperglycemic patients results in glucose-accelerated diuresis, with approximately 300 mL of each liter infused being taken up intracellularly, but this mechanism alone cannot normalize severe hyperglycemia. 2
Clinical Evidence from Stroke Management
The GIST-UK trial demonstrated that glucose-potassium-insulin (GKI) infusions achieved euglycemia at significantly lower levels than saline hydration alone in acute stroke patients with hyperglycemia. 3
Saline-treated patients showed spontaneous glucose decline but failed to achieve optimal glycemic targets, with the mean glucose difference between insulin-treated and saline groups being only 10 mg/dL—insufficient for therapeutic benefit. 1
When Insulin is Mandatory
Diabetic Ketoacidosis and HHS
In hyperglycemic crises (DKA/HHS), continuous intravenous insulin at 0.1 U/kg/h is the treatment of choice after excluding hypokalemia, with saline serving only as adjunctive fluid therapy. 1
The protocol requires insulin infusion to decrease plasma glucose at 50-75 mg/dL/h, with saline addressing volume depletion but not directly correcting hyperglycemia. 1
Once plasma glucose reaches 250 mg/dL in DKA or 300 mg/dL in HHS, insulin should be continued at reduced rates (0.05-0.1 U/kg/h) with dextrose added to prevent hypoglycemia while continuing to clear ketosis. 1
Hospitalized Patients
For hospitalized elderly patients with hyperglycemia, basal insulin regimens (0.1-0.15 units/kg/day) combined with correctional insulin are recommended rather than relying on fluid therapy alone. 1
Sliding-scale insulin alone is inadequate; basal insulin with supplemental rapid-acting analogs for glucose >180 mg/dL provides superior glycemic control and reduces complications compared to reactive approaches. 1
Appropriate Role of Saline
Initial Fluid Resuscitation
In hyperglycemic crises, initial fluid therapy with 0.9% NaCl at 15-20 mL/kg/h (or 1-1.5 L in the first hour) is critical for hemodynamic stabilization before insulin therapy. 1
After initial resuscitation, fluid choice depends on corrected sodium: if normal or elevated, switch to 0.45% NaCl at 4-14 mL/kg/h; if low, continue 0.9% NaCl. 4
The goal is to decrease serum osmolality by no more than 3 mOsm/kg/h to prevent cerebral edema, which requires careful fluid management alongside insulin therapy. 1, 4
Common Pitfall to Avoid
Never use 0.9% NaCl as monotherapy expecting significant glucose reduction—this approach delays definitive treatment and prolongs hyperglycemia, potentially worsening outcomes. 1
In hypernatremic hyperglycemia, avoid normal saline entirely as primary fluid; use D5W to address free water deficit while insulin corrects hyperglycemia. 5
Glycemic Targets During Treatment
Maintain blood glucose 140-180 mg/dL in hospitalized patients per American Diabetes Association recommendations, which requires insulin therapy, not saline alone. 1
For patients with type 2 diabetes, target HbA1c <7.0% with mean plasma glucose 150-160 mg/dL, fasting <130 mg/dL, and postprandial <180 mg/dL—achievable only with pharmacologic intervention. 1