What does a blood ketone concentration of 0.9 mmol/L indicate and how should it be managed?

Blood Ketone Level of 0.9 mmol/L: Clinical Significance and Management

A blood ketone concentration of 0.9 mmol/L represents mild ketonemia that warrants close monitoring and implementation of sick day rules, particularly in individuals with diabetes or those taking SGLT2 inhibitors, though it does not yet meet criteria for diabetic ketoacidosis.

Understanding the Clinical Context

Normal vs. Elevated Ketone Levels

• Ketone bodies are normally present in blood at very low concentrations (<0.5 mmol/L) and serve as an alternative energy source when glucose availability is limited 1
• A level of 0.9 mmol/L represents mild elevation above normal baseline but remains below the threshold for diabetic ketoacidosis (DKA), which requires ketones >3.0 mmol/L 1
• β-hydroxybutyrate (βHB) is the predominant ketone body measured in blood and provides the most accurate assessment of ketone status 2, 3

Physiologic vs. Pathologic Ketonemia

• Mild ketonemia (0.6-1.5 mmol/L) can occur physiologically during fasting, prolonged exercise, pregnancy, or consumption of ketogenic diets 2, 4
• In individuals with diabetes, this level suggests early metabolic stress with relative insulin deficiency and increased counterregulatory hormones 1
• Caution is particularly warranted at βHB levels ≥0.6 mmol/L in the context of physical activity or illness, as this may signal inadequate insulin availability 1

Immediate Assessment and Action

Risk Stratification

• Check blood glucose immediately—the combination of hyperglycemia (>250 mg/dL) with ketones 0.9 mmol/L indicates evolving metabolic decompensation requiring urgent intervention 1
• Assess for symptoms of ketosis including abdominal pain, nausea, vomiting, or altered mental status 1
• Identify precipitating factors: illness, inadequate insulin dosing, SGLT2 inhibitor use, prolonged fasting, or recent surgery 1

SGLT2 Inhibitor Considerations

• If the patient is taking an SGLT2 inhibitor, temporarily withhold the medication immediately, as these agents predispose to euglycemic ketoacidosis where glucose may be normal (<11.0 mmol/L) despite dangerous ketone elevation 1
• SGLT2 inhibitors should be withheld during illness, excessive exercise, prolonged fasting, or surgical procedures 1
• Ketone levels can rise rapidly to >3.0 mmol/L in SGLT2 inhibitor users due to altered insulin/glucagon ratios and increased physiological stress 1

Management Protocol

Sick Day Rules Implementation

• Continue insulin administration—never omit insulin in type 1 diabetes, even during illness 1
• Increase oral fluid intake to prevent dehydration, using sodium-containing fluids such as broth or sports drinks 1
• Ingest 150-200 g of carbohydrate daily (45-50 g every 3-4 hours) to prevent starvation ketosis, using liquid or soft foods if regular meals are not tolerated 1
• Monitor blood glucose and blood ketones every 2-4 hours 1

Insulin Adjustment

• Administer supplemental rapid-acting insulin if blood glucose is elevated (typically 10-20% of total daily dose) 1
• For type 1 diabetes with ketones 0.9 mmol/L and hyperglycemia, consider additional insulin correction doses while maintaining basal insulin 1
• Do not reduce insulin doses during illness or ketosis, as this will worsen metabolic decompensation 1

Monitoring Thresholds for Escalation

• Recheck blood ketones in 2-4 hours after initial interventions 1
• Seek immediate medical attention if ketones rise to ≥1.5 mmol/L, if vomiting prevents oral intake, or if mental status changes occur 1
• Present to emergency department if ketones reach ≥3.0 mmol/L or if venous pH drops below 7.3, as these define DKA requiring intravenous therapy 1

Special Populations

Children and Adolescents

• Youth with type 1 diabetes should postpone intense physical activity when ketones are ≥0.6 mmol/L, particularly if glucose is >350 mg/dL (19.4 mmol/L) 1
• Parents and caregivers should receive education on checking blood ketones during illness and implementing sick day protocols 1
• Blood ketone testing is preferred over urine ketone testing in children, as it improves compliance and reduces emergency department visits 1

Perioperative Setting

• Withhold SGLT2 inhibitors at least 2 days before elective surgery and measure both glucose and ketones on hospital admission 1
• Proceed with surgery only if the patient is clinically well and ketones are <1.0 mmol/L 1
• Restart SGLT2 inhibitors only after the patient is eating and drinking normally postoperatively 1

Common Pitfalls to Avoid

• Do not rely on urine ketone testing alone, as it measures acetoacetate rather than βHB and may show increasing levels even as DKA resolves 1, 2
• Do not assume normal glucose excludes significant ketosis—euglycemic ketoacidosis can occur, particularly with SGLT2 inhibitor use 1
• Do not delay seeking medical care if symptoms worsen or ketones continue rising despite home management 1
• Do not discontinue insulin in attempt to prevent hypoglycemia during illness, as this precipitates DKA 1