What is the recommended initial work‑up for a patient with suspected diabetic ketoacidosis?

Initial Work-Up for Suspected Diabetic Ketoacidosis

Obtain a complete metabolic panel, venous blood gases, complete blood count, urinalysis, serum ketones (preferably β-hydroxybutyrate), and electrocardiogram immediately upon presentation. 1

Core Diagnostic Laboratory Tests

Essential Immediate Labs

• Blood glucose – must be measured stat; classic DKA requires >250 mg/dL, though euglycemic DKA (glucose <200–250 mg/dL) is increasingly recognized, especially with SGLT2 inhibitor use 1, 2
• Venous pH – required for diagnosis; DKA is defined by pH <7.3 1, 2
• Serum bicarbonate – must be <15 mEq/L for DKA diagnosis (mild DKA: 15–18 mEq/L; moderate: 10–15 mEq/L; severe: <10 mEq/L) 1
• Serum electrolytes with calculated anion gap – anion gap should be >10–12 mEq/L in DKA; calculate as [Na⁺] – ([Cl⁻] + [HCO₃⁻]) 1, 2
• Serum ketones – direct measurement of β-hydroxybutyrate in blood is strongly preferred over nitroprusside-based urine or serum tests, which only detect acetoacetate and acetone and completely miss β-OHB, the predominant ketone body 1, 3, 4

Additional Required Initial Labs

• Complete blood count with differential – to assess for infection, leukocytosis, or hemoconcentration 2, 5
• Blood urea nitrogen and creatinine – to evaluate renal function and degree of dehydration 1, 2
• Serum osmolality (or calculate effective osmolality: 2 × [Na] + glucose/18) – to distinguish DKA from hyperosmolar hyperglycemic state and assess severity 1, 2
• Urinalysis with urine ketones – though blood β-OHB is preferred for diagnosis and monitoring 1, 2
• Electrocardiogram – to assess for myocardial infarction (a common precipitant), evaluate potassium effects, and rule out arrhythmias 2, 5
• HbA1c – to distinguish acute versus chronic poor glycemic control 1

Corrected Sodium Calculation

• Correct serum sodium for hyperglycemia by adding 1.6 mEq/L for every 100 mg/dL glucose above 100 mg/dL to the measured sodium value 1, 2
• This corrected sodium guides subsequent fluid choice after the initial hour of isotonic saline 1, 2

Severity Classification

Once labs return, classify DKA severity to guide monitoring intensity:

• Mild DKA: pH 7.25–7.30, bicarbonate 15–18 mEq/L, alert mental status 1
• Moderate DKA: pH 7.00–7.24, bicarbonate 10–15 mEq/L, drowsy mental status 1
• Severe DKA: pH <7.00, bicarbonate <10 mEq/L, stupor or coma – requires intensive monitoring including possible central venous and intra-arterial pressure monitoring 1

Identification of Precipitating Causes

Obtain Cultures When Infection Suspected

• Blood, urine, and throat cultures if infection is suspected, as infection is the most frequent precipitating factor 1, 2, 5
• Administer appropriate antibiotics promptly if infection is identified 1, 2

Consider Additional Testing Based on Clinical Presentation

• Chest X-ray if clinically indicated (pneumonia, aspiration) 5
• Troponin and creatine kinase if myocardial infarction is suspected 2, 6
• Amylase and lipase if pancreatitis is suspected 2, 6
• Hepatic transaminases if indicated 6
• Blood lactate to distinguish lactic acidosis from DKA 1
• Toxic ingestion screen (salicylate, methanol, ethylene glycol) if history or anion gap suggests 1

Common Precipitating Factors to Investigate

• Infection (most common) 2, 5
• Insulin omission or inadequacy 1, 2
• Myocardial infarction 1, 2, 7
• Cerebrovascular accident 1, 2
• SGLT2 inhibitor use (can cause euglycemic DKA) 1, 2, 6
• Pancreatitis 1, 2
• Trauma 1
• Alcohol abuse 2
• Glucocorticoid therapy 2
• Pregnancy 1

Critical Pitfalls to Avoid in Initial Work-Up

• Do not rely on urine ketones or nitroprusside-based tests for diagnosis or monitoring – they miss β-hydroxybutyrate, the predominant and strongest ketoacid in DKA 1, 4
• Do not assume hyperglycemia is always present – euglycemic DKA (glucose <200–250 mg/dL) is increasingly common, especially with SGLT2 inhibitors, pregnancy, reduced oral intake, or concurrent insulin use 1, 2, 6
• Do not overlook potassium levels – despite total body potassium depletion of 3–5 mEq/kg, initial serum potassium may appear normal or even elevated due to acidosis and insulin deficiency 1, 7
• Do not miss myocardial infarction – it can both precipitate and be masked by DKA; maintain high suspicion in appropriate clinical contexts 2, 7
• Do not forget to calculate the anion gap – it confirms the diagnosis and helps monitor resolution 1, 2

Monitoring Frequency During Treatment

• Draw blood every 2–4 hours to measure serum electrolytes, glucose, BUN, creatinine, osmolality, and venous pH until the patient is metabolically stable 1, 2, 5
• Venous pH is adequate for monitoring after initial diagnosis; repeated arterial blood gases are generally unnecessary 1
• β-hydroxybutyrate should be monitored every 2–4 hours during treatment, as ketonemia clears more slowly than hyperglycemia 1