What does it mean to have ketones in my urine?

Ketones in Urine: Significance and Management

The presence of ketones in urine indicates increased fatty acid metabolism and may suggest impending or established diabetic ketoacidosis (DKA), especially in individuals with diabetes, although it can also represent normal physiological responses in certain situations like fasting or pregnancy. 1, 2

What Causes Ketones in Urine?

• Ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone) are produced by the liver when the body shifts to fat metabolism as an alternative energy source when glucose is not readily available 3
• Ketones are normally present in blood and urine but usually at concentrations below detection limits of routine testing methods 1
• Common causes of ketones in urine include:
  • Diabetes with insufficient insulin (especially type 1 diabetes) 1, 2
  • Fasting or prolonged periods without eating 1, 4
  • Pregnancy (found in up to 30% of first morning urine specimens) 1, 4
  • Low-carbohydrate diets 5
  • Prolonged exercise 3

Clinical Significance in Different Scenarios

For People with Diabetes:

• Elevated ketones suggest insufficient insulin and may indicate impending or established diabetic ketoacidosis (DKA), which is a medical emergency 1, 2
• Even mild ketosis (1+ ketones) requires monitoring and potential intervention in ketosis-prone individuals 1
• Patients with type 1 diabetes should test for ketones during acute illness or stress 1
• Individuals treated with SGLT2 inhibitors are at increased risk for DKA, even with relatively normal blood glucose levels (euglycemic DKA) 2

For People without Diabetes:

• Ketones may represent a normal physiological response to fasting 1, 4
• Starvation ketosis typically produces less severe acidosis than diabetic ketoacidosis 4
• Positive ketone readings are found in up to 30% of first morning urine specimens during pregnancy 1

Limitations of Urine Ketone Testing

• Urine dipsticks use the nitroprusside reaction, which only detects acetoacetate and not beta-hydroxybutyrate (the predominant ketone body in DKA) 1, 4, 5
• This limitation can lead to underestimation of total ketone body concentration 4
• False-positive results can occur with:
  • Highly colored urine 1, 4
  • 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 1

Management Recommendations

For People with Diabetes:

• 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, 6
• For patients with normal blood glucose but elevated ketones, consuming some carbohydrates along with insulin may help suppress ketone production 1
• Seek medical attention if:
  • Unable to tolerate oral hydration due to vomiting 2
  • Blood glucose levels do not improve with insulin administration 2, 6
  • Altered mental status is present 2
  • Ketone levels continue to increase despite interventions 2

For All Individuals:

• Blood ketone testing is preferred over urine ketone testing as it measures beta-hydroxybutyrate directly 1, 2, 5
• The urine ketone test is highly sensitive (97-98%) for detecting ketonemia, making it useful for ruling out DKA 1, 7
• During treatment of DKA, beta-hydroxybutyrate levels commonly decrease before acetoacetate levels, so urine ketones may appear to worsen even as the condition improves 5

Important Caveats

• Hypoalbuminemia (serum albumin <3.0 g/dL) is associated with increased risk of ketosis in hospitalized patients with type 2 diabetes 8
• Currently available urine ketone tests are not reliable for diagnosing or monitoring treatment of ketoacidosis 1
• At least one urinary ketone measurement should be considered in all severely ill patients when the underlying pathological process is not fully understood 9