What does the laboratory abbreviation UKB (urinary ketone bodies) mean and when should it be ordered?

Understanding UKB (Urinary Ketone Bodies) in Laboratory Testing

What UKB Means

UKB stands for urinary ketone bodies—a laboratory test that detects acetoacetate (and sometimes acetone) in urine using a nitroprusside-based dipstick reaction, but critically, this test does NOT measure β-hydroxybutyrate, which is the predominant ketone body in pathological ketosis. 1

The three ketone bodies are:

• β-hydroxybutyrate (BOHB) – the predominant ketone in diabetic ketoacidosis 1
• Acetoacetate (AcAc) – what urine dipsticks actually detect 1
• Acetone – formed from spontaneous decarboxylation of acetoacetate 1, 2

When to Order UKB Testing

High-Priority Indications (Immediate Testing Required)

Order UKB or preferably blood ketones immediately in these scenarios:

• Type 1 diabetes patients with unexplained hyperglycemia (>300 mg/dL) or any acute illness 1, 3
• Any diabetic patient on SGLT2 inhibitors presenting with illness, nausea, or abdominal pain—even with normal glucose—because these drugs cause euglycemic DKA 1, 3
• History of prior DKA with current symptoms (nausea, vomiting, abdominal pain, Kussmaul respirations) 1, 3
• Pregnant patients with diabetes experiencing any illness or hyperglycemia 1, 3
• Febrile diabetic patients, since infection precipitates approximately 50% of DKA cases 3, 4

Lower-Priority Indications

• Monitoring compliance with ketogenic diets (<50 g carbohydrate/day) 3, 2
• Evaluating suspected alcoholic ketoacidosis (though hyperglycemia is typically absent) 1
• Assessment during prolonged fasting or starvation states 3, 4

Critical Limitations You Must Know

Why Urine Testing Is Problematic

Blood β-hydroxybutyrate measurement is strongly preferred over urine ketone testing for ALL clinical decision-making because urine dipsticks miss the predominant ketone body and significantly underestimate total ketone burden. 1, 3

Specific problems with UKB:

• Sensitivity as low as 35-52% for mild-to-moderate ketosis 3
• Cannot be used to monitor DKA treatment because BOHB falls while acetoacetate rises during successful therapy, causing persistently positive urine tests despite clinical improvement 1, 3
• Up to 30% of healthy individuals show positive first-morning urine ketones after overnight fasting—this is physiologically normal 1, 3

False Results

False-positive: Sulfhydryl-containing medications (e.g., captopril) 3, 5, 4

False-negative:

• Test strips exposed to air for prolonged periods 3
• Highly acidic urine (e.g., after large ascorbic acid intake) 3, 4

Interpretation Algorithm

Step 1: Check Blood Glucose Immediately

• Glucose >250 mg/dL + positive ketones = medical emergency requiring full DKA workup 3, 5
• Normal glucose + positive ketones = likely benign (starvation, fasting, ketogenic diet) 3, 4

Step 2: If Blood Ketone Testing Available (Preferred)

Action thresholds for blood BOHB: 3, 5

• <0.5 mmol/L: No intervention needed
• 0.5-1.5 mmol/L: Initiate sick-day rules (oral hydration, supplemental short-acting insulin with carbohydrates, frequent monitoring)
• ≥1.5 mmol/L: Seek immediate medical attention; IV insulin typically required

Step 3: Confirm DKA Diagnosis (All Criteria Required)

DKA is confirmed ONLY when all of the following are present: 1, 3, 5

• Plasma glucose >250 mg/dL
• Arterial pH <7.30
• Serum bicarbonate <15 mEq/L
• Positive ketones (urine or blood)
• Anion gap >10 mEq/L

Common Pitfalls to Avoid

1. Never rely on urine ketones alone to diagnose DKA—you need arterial pH, bicarbonate, and anion gap 1

2. Never use urine ketones to monitor DKA treatment response—they will paradoxically worsen as the patient improves 1, 3

3. Don't assume normal glucose excludes DKA in SGLT2 inhibitor users—euglycemic DKA (glucose <250 mg/dL) is common in this population 1, 3

4. Don't panic over trace morning ketones in healthy individuals—up to 30% of first-morning specimens are positive after overnight fasting 1, 3

5. Don't discontinue basal insulin even if the patient isn't eating—this worsens ketosis 3

Practical Recommendation

In 2024, if you have access to point-of-care blood BOHB meters, order blood ketones instead of UKB for any clinical decision-making. 1, 3 Reserve urine ketone testing only for home monitoring in stable diabetic patients or when blood testing is unavailable, and always interpret positive results in the context of blood glucose, symptoms, and clinical presentation. 1, 3