USMLE Prep - Medical Reference Library

Diabetic Ketoacidosis — Fluids, Insulin Protocol, and Potassium Strategy

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

Synopsis:

DKA presents with hyperglycemia, anion gap metabolic acidosis, and ketonemia/ketonuria. Begin isotonic fluids, correct potassium before insulin if K+ <3.3, start insulin infusion when safe, and transition to subcutaneous insulin once gap closes. Identify and treat precipitants.

Key Points

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

Algorithm

  1. Start fluids; check K+. If K+ <3.3 → replete before insulin.
  2. Begin insulin infusion; add dextrose when glucose ~200 mg/dL to continue ketone clearance.
  3. Replace K+/Mg2+/phosphate as needed; monitor glucose/electrolytes closely.
  4. Identify and treat precipitant (infection, insulin omission, MI); transition to SC insulin when AG closed and patient eating.

Clinical Synopsis & Reasoning

DKA presents with hyperglycemia, anion gap metabolic acidosis, and ketonemia/ketonuria. Begin isotonic fluids, correct potassium before insulin if K+ <3.3, start insulin infusion when safe, and transition to subcutaneous insulin once gap closes. Identify and treat precipitants.


Treatment Strategy & Disposition

Stabilize ABCs. Initiate guideline‑concordant first‑line therapy with precise dosing and continuous monitoring. Escalate to advanced/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
BMP, anion gap, β-hydroxybutyrate/ketonesDiagnosis/severityHigh anion gap, ketonemiaTrend closure
VBG/ABG and calculated serum osmolalityAcid-baseAcidemia; HHS overlapGuide therapy
Electrolytes (K+, Mg2+, phosphate) and glucose hourlySafetyHypokalemia risk during therapyReplete proactively

High-Risk & Disposition Triggers

TriggerWhy it mattersAction
K+ <3.3 mEq/L or severe acidosis (pH <7.0)Arrhythmia/respiratory failure riskHold insulin; replete K+ aggressively; ICU
Cerebral edema signs (headache, AMS, bradycardia)Life-threatening complicationHypertonic saline/mannitol; neuro consult; imaging
Refractory hypotension or hypoxemiaShock/ARDS riskICU; vasopressors; ventilatory support
Pregnancy or severe comorbidityFetal/maternal riskMultidisciplinary care; fetal monitoring
Failure of anion gap to close or rising β‑hydroxybutyrateTreatment failureReassess insulin/fluids; search precipitant

Pharmacology

Medication/InterventionMechanismOnsetRole in TherapyLimitations
Normal saline or balanced crystalloids (1–1.5 L in first hour)ResuscitationImmediateRestore volumeSwitch based on Na+/osmolality
Regular insulin: 0.1 U/kg IV bolus then 0.1 U/kg/h infusion (or no bolus with 0.14 U/kg/h)InsulinMinutesStop ketogenesisAdd dextrose when glucose ~200 mg/dL
Potassium chloride per protocol (10–20 mEq/h)ElectrolyteHoursKeep K+ 4.0–5.0Hold insulin if K+ <3.3
Phosphate repletion (selected)ElectrolyteHoursIf severe hypophosphatemia or respiratory/cardiac dysfunction
Bicarbonate (rare; pH <6.9)BufferImmediateSevere acidosis onlyControversial

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. ADA/Endocrine Society consensus on DKA/HHS management — Link