What is the initial workup for a patient with suspected diabetic ketoacidosis?

Initial Workup for Diabetic Ketoacidosis

Obtain a complete metabolic panel, venous blood gas, complete blood count with differential, urinalysis, serum β-hydroxybutyrate, and electrocardiogram immediately upon presentation of suspected DKA. 1, 2

Essential Laboratory Tests

Immediate Bedside/Stat Tests

• Blood glucose – confirms hyperglycemia (typically >250 mg/dL, though euglycemic DKA can occur with glucose <200–250 mg/dL) 1, 2, 3
• Venous blood gas – measures pH and bicarbonate to assess acidosis severity; DKA requires pH <7.3 and bicarbonate <15 mEq/L 1, 2, 3
• Serum β-hydroxybutyrate (β-OHB) – this is the gold standard and preferred method for diagnosing and monitoring DKA, as it directly measures the predominant ketone body 1, 2, 4

Core Metabolic Panel

• Serum electrolytes (sodium, potassium, chloride, bicarbonate) – essential for calculating anion gap and guiding electrolyte replacement 1, 2, 3
• Anion gap calculation using [Na⁺] - ([Cl⁻] + [HCO₃⁻]) – should be >10–12 mEq/L in DKA 1, 2, 3
• Corrected sodium – add 1.6 mEq/L for every 100 mg/dL glucose above 100 mg/dL to assess true sodium status 1, 2, 3
• Blood urea nitrogen and creatinine – assess renal function and hydration status 1, 2, 3
• Serum osmolality – evaluate hyperosmolar state; calculate effective osmolality as 2 × [Na] + glucose/18 1, 2, 3

Additional Essential Tests

• Complete blood count with differential – identify infection or other precipitating factors 1, 2, 3
• Urinalysis with urine dipstick – screen for infection and assess ketonuria (though not for monitoring treatment) 1, 2
• Electrocardiogram – detect cardiac complications and monitor for potassium-related arrhythmias 1, 2, 3
• HbA1c – distinguish acute decompensation in well-controlled diabetes from chronic poor control 1, 2

Severity Classification Based on Initial Labs

Mild DKA: venous pH 7.25–7.30, bicarbonate 15–18 mEq/L, anion gap >10 mEq/L, alert mental status 1, 2

Moderate DKA: venous pH 7.00–7.24, bicarbonate 10–15 mEq/L, anion gap >12 mEq/L, drowsy mental status 1, 2

Severe DKA: venous pH <7.00, bicarbonate <10 mEq/L, anion gap >12 mEq/L, stupor/coma – requires intensive monitoring including possible central venous and intra-arterial pressure monitoring 1, 2

Identifying Precipitating Factors

Obtain Cultures When Infection Suspected

• Blood, urine, and throat cultures – infection is the most frequent precipitating factor for DKA 1, 2, 3
• Administer appropriate antibiotics promptly if infection is identified 1, 3

Consider Additional Testing Based on Clinical Presentation

• Troponin and creatine kinase – myocardial infarction can both precipitate and be masked by DKA 2, 3, 5
• Amylase and lipase – evaluate for pancreatitis as a precipitating cause 3, 5
• Hepatic transaminases – assess for concurrent hepatic pathology 5
• Chest radiography – identify pneumonia or other pulmonary pathology 5
• Blood lactate – distinguish lactic acidosis from DKA 2

Critical Pitfalls to Avoid in Initial Workup

Never delay potassium measurement – if initial potassium is <3.3 mEq/L, delay insulin and aggressively replace potassium first to prevent fatal arrhythmias, cardiac arrest, and respiratory muscle weakness 1, 2, 3

Do not rely on urine ketones for diagnosis or monitoring – nitroprusside-based tests (urine dipsticks and some serum assays) only detect acetoacetate and acetone, completely missing β-hydroxybutyrate, which is the predominant and strongest ketoacid in DKA 1, 2, 4

Do not assume normal temperature rules out infection – patients with DKA can be normothermic or hypothermic despite serious infection, and hypothermia is a sign of poor prognosis 2

Recognize euglycemic DKA – particularly in patients on SGLT2 inhibitors, pregnant women, or those with reduced oral intake; glucose may be <200–250 mg/dL despite severe ketoacidosis 1, 3, 5

Monitoring Strategy After Initial Workup

• Draw blood every 2–4 hours during treatment to measure electrolytes, glucose, BUN, creatinine, osmolality, and venous pH 1, 3
• Monitor β-hydroxybutyrate every 2–4 hours alongside other parameters, as ketonemia takes longer to clear than hyperglycemia 1
• Venous pH suffices for monitoring after initial diagnosis; repeated arterial blood gases are generally unnecessary, as venous pH is typically 0.03 units lower than arterial 1, 3