What does the presence of 1+ ketones in the urine indicate?

Significance of 1+ Ketones in Urine

The presence of 1+ ketones in urine indicates mild ketosis, which may suggest impending diabetic ketoacidosis (DKA) in high-risk individuals (especially those with type 1 diabetes), or could represent a normal physiological response to fasting, pregnancy, or low-carbohydrate diets in otherwise healthy individuals. 1

Clinical Significance of Urine Ketones

• Ketone bodies (acetoacetate, β-hydroxybutyrate, and acetone) are normally present in urine and blood but usually at concentrations below detection limits of routine testing methods 1
• Positive ketone readings can be found in normal individuals during fasting and in up to 30% of first morning urine specimens from pregnant women 1
• In diabetic patients, especially those with type 1 diabetes, elevated ketones suggest insufficient insulin and may indicate impending or established diabetic ketoacidosis (DKA), which is a medical emergency 1
• The presence of urine ketones is highly sensitive for DKA with high negative predictive value, making it useful for ruling out DKA 1

Interpretation of 1+ Ketones in Different Clinical Scenarios

In Diabetic Patients:

• For ketosis-prone individuals (type 1 diabetes, history of DKA, or those on SGLT2 inhibitors), even mild ketosis requires monitoring and potential intervention 2
• Patients with type 1 diabetes should test for ketones during:
  • Acute illness or stress 1
  • When blood glucose levels are consistently elevated (>300 mg/dl) 1
  • During pregnancy 1
  • When symptoms of ketoacidosis (nausea, vomiting, abdominal pain) are present 1

In Non-Diabetic Individuals:

• 1+ ketones may represent:
  • Normal physiological response to fasting 1
  • Response to a low-carbohydrate diet 3
  • Normal finding in up to 30% of first morning urine specimens from pregnant women 1

Management Recommendations

For Diabetic Patients:

• Increase oral fluid intake to prevent dehydration 2
• Monitor blood glucose and ketone levels every 3-4 hours 2
• Consider additional short or rapid-acting insulin if ketone levels increase or symptoms develop 2
• For patients with normal blood glucose but elevated ketones, consuming some carbohydrates along with insulin may help suppress ketone production 2
• If ketone levels increase above 1.5 mmol/L despite interventions, or if symptoms of ketoacidosis develop, seek medical advice 2

For All Patients:

• Blood ketone testing is preferred over urine ketone testing as it measures β-hydroxybutyrate directly, which is the predominant ketone body in DKA 1
• Urine ketone tests using nitroprusside-containing reagents only detect acetoacetate and not β-hydroxybutyrate 1

Important Caveats and Limitations

• False-positive urine ketone results can occur with:
  • Highly colored urine 1
  • Several sulfhydryl drugs, including the antihypertensive drug captopril 1
• False-negative readings can occur when:
  • Test strips have been exposed to air for an extended period 1
  • Urine specimens are highly acidic (such as after large intakes of ascorbic acid) 1
• During DKA resolution, urine ketone levels may appear to increase even as the condition improves, because β-hydroxybutyrate (predominant in blood) is converted to acetoacetate (predominant in urine) 3
• Currently available urine ketone tests are not reliable for diagnosing or monitoring treatment of ketoacidosis 1

Correlation Between Urine and Blood Ketones

• Urine ketones scored as + (1+) correspond to median capillary blood ketone levels of approximately 0.5 mmol/L 4
• Good correlation exists between urine ketones and capillary blood ketones for low values, but poor correlation for high values 4
• Blood ketone testing methods that quantify β-hydroxybutyric acid are preferred over urine ketone testing for diagnosing and monitoring ketoacidosis 1