What are the implications and necessary actions if ketones are present in urine?

Ketones in Urine: Implications and Actions

The presence of ketones in urine requires immediate attention as it may indicate impending or established diabetic ketoacidosis (DKA), a potentially life-threatening condition requiring immediate medical intervention, especially in patients with type 1 diabetes, pregnancy with pre-existing diabetes, or those taking SGLT2 inhibitors. 1

Clinical Significance of Urinary Ketones

Normal vs. Abnormal Findings

• Ketones are normally present in urine but usually below detectable limits with routine testing methods 1
• Positive ketone readings can occur in:
  • Normal individuals during fasting (up to 30% of first morning specimens from pregnant women) 1
  • After hypoglycemia 1
  • During starvation 1
  • With very low-carbohydrate (ketogenic) diets 1

High-Risk Populations

Ketone testing is particularly important for:

• Type 1 diabetes patients 1
• Pregnant women with pre-existing diabetes or gestational diabetes 1
• Patients taking SGLT2 inhibitors (which increase DKA risk even in type 2 diabetes) 1
• Patients with a history of DKA 1

Action Algorithm Based on Urinary Ketones

For Patients with Diabetes:

1. If ketones are present with hyperglycemia (>300 mg/dL or 16.7 mmol/L):

   • Implement sick day rules immediately 1
   • Increase fluid intake to prevent dehydration 1
   • Take additional short/rapid-acting insulin as prescribed 1
   • Monitor blood glucose and ketones frequently 1
   • Seek immediate medical attention if:
     • Vomiting occurs
     • Ketone levels increase despite treatment
     • Mental status changes
     • Symptoms of DKA appear (nausea, vomiting, abdominal pain) 1

2. If ketones are present with normal blood glucose:

   • In patients on SGLT2 inhibitors: This may represent euglycemic DKA - seek medical attention 1
   • In other patients: Increase carbohydrate intake and hydration 1

3. If ketones are present during illness/stress:

   • Monitor more frequently
   • Follow sick day protocol
   • Contact healthcare provider if levels don't improve 1

For Non-Diabetic Individuals:

• If found incidentally: Consider fasting state, pregnancy, or low-carbohydrate diet as potential causes 1
• If accompanied by symptoms (nausea, vomiting, abdominal pain): Evaluate for undiagnosed diabetes or other metabolic disorders 1

Testing Considerations and Limitations

Testing Methods

• Urine ketone tests use nitroprusside-containing reagents that detect acetoacetate and acetone, but not β-hydroxybutyrate (the predominant ketone in DKA) 1
• Blood ketone testing that measures β-hydroxybutyrate is preferred for diagnosing and monitoring DKA 1

Important Limitations

• False positives can occur with:

  • Highly colored urine 1
  • Certain medications (e.g., captopril and other sulfhydryl drugs) 1

• False negatives can occur with:

  • Test strips exposed to air for extended periods 1
  • Highly acidic urine (e.g., after large intake of ascorbic acid) 1
  • DKA in treatment phase (as β-hydroxybutyrate converts to acetoacetate) 2

Clinical Pearls

1. Urine ketone tests are highly sensitive for detecting ketonemia in DKA (97% sensitivity) but should not be relied upon alone for diagnosis 3

2. For diagnosis and monitoring of DKA, blood ketone measurements of β-hydroxybutyrate are more reliable than urine ketone tests 1

3. During DKA treatment, urine ketones may paradoxically increase even as the condition improves, because β-hydroxybutyrate (not measured by urine tests) is converted to acetoacetate (which is measured) 2

4. Ketone testing materials should be available in all clinical settings treating patients with diabetes 1

5. Regular aerobic exercise may be associated with the presence of urinary ketones in otherwise healthy individuals 4

By understanding the significance of ketones in urine and taking appropriate action, healthcare providers can help prevent the progression to severe DKA and improve patient outcomes.