Essential Laboratory Tests for Diagnosing and Managing Diabetic Ketoacidosis (DKA)
Blood β-hydroxybutyrate (bOHB) measurement is the most accurate method for diagnosing DKA and should be the primary test used for both diagnosis and monitoring of treatment. 1, 2
Core Diagnostic Tests for DKA
- Blood glucose measurement is essential, though hyperglycemia (>250 mg/dL) has been de-emphasized in recent guidelines due to the increasing incidence of euglycemic DKA 3
- Blood β-hydroxybutyrate (bOHB) measurement is superior to urine ketones and should be used for diagnosis of DKA 1, 2
- Venous pH measurement with a value <7.3 is diagnostic for DKA 1, 2
- Serum bicarbonate measurement with a value <18 mEq/L is diagnostic for DKA 1, 2
- Serum electrolytes to calculate anion gap (>10 mEq/L indicates DKA) and assess electrolyte imbalances 1, 2
Additional Essential Laboratory Tests
- Blood urea nitrogen (BUN) and creatinine to assess renal function and dehydration status 1, 3
- Complete blood count with differential to evaluate for infection or other complications 3
- Urinalysis to check for infection and confirm ketones (though less reliable than blood bOHB) 3
- Potassium levels must be monitored closely when insulin is administered, especially intravenously, due to risk of hypokalemia 4
- HbA1c to assess long-term glycemic control and determine if this is new-onset or poorly controlled diabetes 3
Why Blood β-hydroxybutyrate Testing is Superior
- bOHB is the predominant ketone body in DKA, making its direct measurement more accurate 1, 2
- Blood bOHB testing can detect ketosis earlier than traditional nitroprusside methods 2
- Specific measurement of bOHB should be used for both diagnosis and monitoring during treatment 1
- Blood ketone determinations that rely on the nitroprusside reaction should NOT be used to monitor treatment of DKA as they only measure acetoacetate and acetone, not bOHB 1, 2
Limitations of Urine Ketone Testing
- Urine ketone testing has limited ability to quantify the degree of ketosis 2
- Nitroprusside method only measures acetoacetate and acetone, not bOHB, which can lead to inaccurate diagnosis 1, 2
- Urine ketones may remain positive long after serum ketones have cleared, making them unreliable for monitoring treatment 1
Monitoring During DKA Treatment
- Blood glucose, electrolytes, BUN, creatinine, venous pH, and anion gap should be monitored every 2-4 hours during treatment 2
- Blood bOHB is the preferred method for monitoring ketosis resolution during treatment 1, 2
- Potassium levels require close monitoring due to risk of hypokalemia during insulin therapy 4
Criteria for DKA Resolution
- Glucose <200 mg/dL 2
- Serum bicarbonate ≥18 mEq/L 2
- Venous pH >7.3 2
- Anion gap ≤12 mEq/L 2
- Reduction in blood bOHB levels 1, 2
Common Pitfalls to Avoid
- Relying solely on urine ketones for diagnosis or monitoring can lead to inaccurate assessment 1, 2
- Failing to recognize euglycemic DKA, especially in patients taking SGLT2 inhibitors 1, 3, 5
- Not monitoring potassium levels closely during insulin therapy, which can lead to dangerous hypokalemia 4
- Using nitroprusside-based blood ketone tests to monitor treatment, as acetoacetate and acetone may increase as bOHB falls during successful therapy 1