What does it mean to have ketones in the urine and how is it treated?

What Ketones in Urine Mean and How to Treat Them

Ketones in urine indicate your body is breaking down fat for energy instead of glucose, which in people with diabetes signals insufficient insulin and potential diabetic ketoacidosis (DKA)—a medical emergency requiring immediate intervention with hydration, insulin, and close monitoring. 1

Clinical Significance

The presence of ketones in urine has different meanings depending on your clinical context:

In people with diabetes (especially type 1):

• Urine ketones are highly sensitive for DKA with high negative predictive value, making them useful for ruling out this life-threatening condition 1
• Even mild ketosis (1+ ketones) may indicate impending DKA in high-risk individuals and requires monitoring and potential intervention 2
• Elevated ketones suggest insufficient insulin levels and represent a warning sign that should not be ignored 2

In non-diabetic individuals:

• Ketones may represent normal physiological responses to fasting or prolonged exercise 2, 3
• Up to 30% of first morning urine specimens from pregnant women show positive ketones as a normal finding 2, 4
• Ketogenic diets intentionally produce physiological ketosis (0.3-4 mmol/L blood ketones) with normal pH and blood glucose 4

Critical Distinction: Physiological vs. Pathological Ketosis

Physiological ketosis is characterized by ketone bodies of 0.3-4 mmol/L, normal pH, low but physiologically normal insulin levels, and normal blood glucose 4

Pathological ketosis (DKA) is characterized by very high ketone bodies (>7-8 mmol/L), low systemic pH, absent or severely deficient insulin, and requires emergency treatment 4

Important Testing Limitations

You must understand that standard urine ketone tests have significant limitations:

• Urine dipsticks using nitroprusside only detect acetoacetate and acetone, but completely miss β-hydroxybutyrate (βOHB), which is the predominant ketone body in DKA 1, 2
• This can underestimate total ketone body concentration and provide misleading clinical information 1
• Urine ketone tests are not reliable for diagnosing or monitoring treatment of ketoacidosis 2
• Blood ketone testing measuring βOHB directly is strongly preferred over urine testing 1, 2, 5

Common causes of false results:

• False-positives occur with highly colored urine or sulfhydryl drugs like captopril 1, 2
• False-negatives occur when test strips are exposed to air for extended periods or when urine is highly acidic 2
• During DKA resolution, urine ketones may paradoxically increase even as the condition improves, because βOHB is oxidized to acetoacetate (which appears in urine) as DKA resolves 3

Treatment Algorithm for People with Diabetes

When you detect ketones in urine, follow these "sick day rules":

Immediate actions:

• Increase oral fluid intake immediately to prevent dehydration 1, 5
• Monitor blood glucose and ketone levels every 3-4 hours 1, 5
• Administer additional short- or rapid-acting insulin if blood glucose is elevated 1, 5
• For normal blood glucose but elevated ketones, consume some carbohydrates along with insulin to help suppress ketone production 2

Seek emergency medical attention if:

• You cannot maintain oral hydration due to vomiting 1, 5
• Mental status changes occur 1, 5
• Ketone levels continue to increase despite interventions 1, 5
• Symptoms worsen (abdominal pain, nausea, rapid breathing) 5

Special High-Risk Populations

SGLT2 inhibitor users:

• These medications increase risk for euglycemic DKA (DKA with relatively normal blood glucose levels) 5, 4
• Ketone testing should be performed during any illness or unexplained symptoms 4

Pregnant individuals:

• May present with euglycemic DKA and should seek immediate medical attention if ketones are elevated 5
• Remember that mild ketonuria can be normal in pregnancy, but clinical context matters 2, 4

Monitoring Recommendations

For ketosis-prone individuals (type 1 diabetes, history of DKA, SGLT2 inhibitor users):

• Check urine or blood ketones during any illness or symptoms of deteriorating glycemic control 1
• Check ketones when blood glucose exceeds your individualized threshold (typically >250 mg/dL) 5
• Blood ketone testing is strongly preferred over urine testing for both diagnosis and monitoring 1, 5

Specific measurement recommendation:

• Blood β-hydroxybutyrate measurement should be used for diagnosis of DKA and may be used for monitoring during treatment 1
• Blood ketone determinations using the nitroprusside reaction should NOT be used to monitor DKA treatment 1

Key Clinical Pitfall to Avoid

Children with type 1 diabetes (and their caregivers) who use blood ketone testing rather than urine testing are more likely to actually measure ketones during illness and have almost half the number of emergency department visits or hospitalizations compared to those using urine testing 1. This demonstrates the practical superiority of blood ketone monitoring in real-world management.