USMLE Prep - Medical Reference Library

Diabetic Ketoacidosis — Fluids, Insulin-Dextrose Pairing, and Electrolytes

System: Endocrinology • Reviewed: Sep 1, 2025 • Step 1Step 2Step 3

Synopsis:

Hyperglycemia, ketonemia, and anion-gap metabolic acidosis. Start isotonic fluids, initiate insulin with potassium-safe thresholds, add dextrose when glucose ~200–250 mg/dL to continue ketone clearance, and correct electrolytes; search for triggers.

Key Points

  • Use the highest‑yield diagnostic test early; do not let testing delay time‑critical therapy.
  • Set objective targets (hemodynamic, neurologic, respiratory) and reassess frequently.
  • Plan definitive source control or reperfusion when indicated; document follow‑up and patient education.

Algorithm

  1. Initial fluids: 15–20 mL/kg 0.9% saline first hour; reassess.
  2. Start insulin infusion when K+ ≥3.3; hold and replete K+ if <3.3.
  3. Add dextrose when glucose 200–250 mg/dL to continue ketone clearance.
  4. Replace K+ aggressively; consider phosphate if severe deficit.
  5. Transition to SC insulin when gap closed and patient eating; address precipitant.

Clinical Synopsis & Reasoning

Hyperglycemia, ketonemia, and anion-gap metabolic acidosis. Start isotonic fluids, initiate insulin with potassium-safe thresholds, add dextrose when glucose ~200–250 mg/dL to continue ketone clearance, and correct electrolytes; search for triggers.


Treatment Strategy & Disposition

Stabilize ABCs. Initiate guideline‑concordant first‑line therapy with precise dosing and continuous monitoring. Escalate to advanced or procedural interventions based on explicit failure criteria. Define ICU, step‑down, and ward disposition triggers; involve specialty teams early.


Epidemiology / Risk Factors

  • Risk varies by comorbidity and precipitants; see citations for condition‑specific data.

Investigations

TestRole / RationaleTypical FindingsNotes
Glucose, BMP, venous blood gasDiagnosis/severityHyperglycemia, low HCO3-, low pHTrack gap closure
Ketones (β-hydroxybutyrate)DiagnosisElevatedTrend with therapy
Electrolytes including phosphate and magnesiumComplication preventionDerangements commonReplace as indicated

Pharmacology

Medication/InterventionMechanismOnsetRole in TherapyLimitations
0.9% Saline → 0.45% based on Na+CrystalloidImmediateRestore volumeAvoid rapid osmolality shifts
Regular insulin infusion 0.1 U/kg/hInsulinMinutesClear ketones and close gapStart when K+ ≥3.3; add dextrose at 200–250 mg/dL
Potassium chlorideElectrolyteImmediateMaintain K+ 4.0–5.0 mEq/LFrequent monitoring
Phosphate (selected)ElectrolyteHoursIf severe hypophosphatemia or respiratory weaknessAvoid hypocalcemia

Prognosis / Complications

  • Outcome depends on timeliness of diagnosis and definitive therapy; monitor for complications.

Patient Education / Counseling

  • Provide red‑flag education, adherence guidance, and explicit return precautions; arrange timely specialty follow‑up.

References

  1. International Consensus on Hyperglycemic Crises in Adults (2024) — Link