What is the management plan for a patient with ketonuria but a normal Venous Blood Gas (VBG) result, suspected of having Diabetic Ketoacidosis (DKA)?

Management of Ketonuria with Normal VBG

This patient does not meet criteria for DKA and should be managed as having starvation ketosis or early ketosis rather than diabetic ketoacidosis. 1

DKA Diagnostic Criteria

The American Diabetes Association requires all three of the following criteria to diagnose DKA 1:

• Blood glucose >250 mg/dL (or >200 mg/dL in some definitions) 1
• Venous pH <7.3 1
• Serum bicarbonate <15 mEq/L (or <18 mEq/L for mild DKA) 1
• Moderate ketonuria or ketonemia 1

A normal VBG (pH ≥7.3 and bicarbonate ≥15-18 mEq/L) excludes the diagnosis of DKA, regardless of ketonuria presence 1. The presence of urine ketones alone is highly sensitive for ruling out DKA when negative, but positive ketones without acidosis do not confirm DKA 2.

Clinical Assessment Algorithm

Step 1: Verify the VBG Results

• Confirm venous pH is truly >7.3 and bicarbonate is >15-18 mEq/L 1
• Calculate the anion gap: [Na⁺] - ([Cl⁻] + [HCO₃⁻]) - should be ≤12 mEq/L if no DKA 1
• Check blood glucose level 1

Step 2: Measure Blood Ketones (β-hydroxybutyrate)

• Direct measurement of β-hydroxybutyrate (β-OHB) in blood is the preferred method rather than relying on urine ketones 2, 1
• Urine ketone strips only detect acetoacetate and acetone, missing β-OHB (the predominant ketone in DKA), leading to misleading results 2, 1
• Normal β-OHB is <0.5 mmol/L; mild elevation is 0.5-1.5 mmol/L; DKA typically shows >3 mmol/L 3

Step 3: Determine the Cause of Ketonuria

Common causes of ketonuria without acidosis include:

• Starvation ketosis - prolonged fasting, inadequate carbohydrate intake, or illness with poor oral intake 4
• Early/mild ketosis - insufficient insulin with compensated metabolic state 2
• Post-exercise ketosis - increased fat metabolism 2
• Pregnancy - accelerated starvation in pregnant women with diabetes 5

Management Plan for Ketonuria Without DKA

Immediate Actions

For patients with ketonuria but normal VBG:

• Ensure adequate hydration - oral fluids if tolerated, 1-2 liters over 2-4 hours 6
• Administer supplemental rapid-acting insulin - give 10-20% of total daily dose subcutaneously 2
• Provide oral carbohydrates - 15-30 grams to suppress ketogenesis while giving insulin 2
• Check blood glucose every 2-4 hours 7
• Recheck blood ketones in 2-4 hours to ensure downward trend 3

Sick Day Management Protocol

The American Diabetes Association recommends the following "sick day rules" for ketosis-prone individuals 2:

• Continue basal insulin - never stop long-acting insulin, even if not eating 7
• Give supplemental rapid-acting insulin - typically 10-20% of total daily dose every 2-4 hours if ketones persist 2
• Maintain hydration - drink 8 oz of sugar-free fluids hourly 2
• Consume small amounts of carbohydrates - 15 grams every 1-2 hours to prevent starvation ketosis 2
• Monitor frequently - check blood glucose and ketones every 2-4 hours 2, 7

Criteria for Emergency Department Evaluation

Send the patient to the ED if any of the following develop:

• Persistent or worsening ketones despite 4-6 hours of treatment 2
• Development of acidosis (pH <7.3 or bicarbonate <18 mEq/L) 1
• Inability to maintain oral hydration due to vomiting 2
• Mental status changes 2
• Blood glucose persistently >300 mg/dL despite supplemental insulin 2
• β-OHB >3 mmol/L 3

Critical Pitfalls to Avoid

Pitfall #1: Over-relying on Urine Ketones

• Urine ketone strips miss β-OHB entirely and can remain positive for 12-24 hours after blood ketones normalize 2, 3
• Always measure blood β-OHB when available rather than urine ketones for accurate assessment 2, 1

Pitfall #2: Stopping Basal Insulin

• Never discontinue long-acting insulin, even if the patient is not eating, as this precipitates DKA in type 1 diabetes 7
• Basal insulin coverage is critical to prevent progression to full DKA 7

Pitfall #3: Treating as DKA When Criteria Not Met

• Do not initiate IV insulin infusion or aggressive IV fluid resuscitation if pH >7.3 and bicarbonate >15-18 mEq/L 1
• Subcutaneous insulin with oral hydration and carbohydrates is appropriate for non-acidotic ketosis 2, 6

Pitfall #4: Missing Euglycemic DKA

• If blood glucose is <250 mg/dL but pH <7.3 with ketones, this is euglycemic DKA and requires full DKA treatment protocol 4
• Check pH and ketones in all ill diabetic patients regardless of glucose level 4

Follow-up and Prevention

• Educate the patient on recognizing early ketosis symptoms (nausea, abdominal pain, fruity breath) 2
• Provide written sick day management instructions 2
• Ensure access to blood ketone meter - patients using blood ketone testing have 50% fewer ED visits compared to urine ketone testing 2
• Review precipitating factors - infection, insulin omission, pump failure, SGLT2 inhibitor use 5, 4