No, calculating a glucose-to-ketone ratio is not a reliable or recommended method to estimate insulin levels in clinical practice.
Routine testing for insulin or proinsulin is not recommended in most people with diabetes or at risk for diabetes, as these assays are useful primarily for research purposes 1. The 2023 American Diabetes Association guidelines explicitly state this recommendation with moderate-level evidence.
Why Insulin Measurement Is Not Clinically Useful
The fundamental problem with measuring insulin levels—whether directly or through calculated ratios—stems from several critical limitations:
Lack of Standardization and Diagnostic Value
- No standardized assays exist for insulin measurement, with poor reproducibility even within the same assay 2
- No well-defined cut points differentiate normal from abnormal insulin levels, unlike glucose or lipids 2
- Fasting insulin concentrations show considerable overlap between insulin-resistant and insulin-sensitive individuals, explaining only 5-50% of variability in insulin sensitivity 2
- Different studies propose insulin resistance cutoffs that vary by 2.5-fold, making any ratio calculation inherently unreliable 2
Physiological Confounders
- Race/ethnicity differences in insulin concentrations occur due to variations in metabolic clearance rates 2
- Cross-reactivity between insulin and proinsulin interferes with measurements 2
- In youth with type 2 diabetes, fasting insulin concentrations are paradoxically higher than in non-diabetics despite severe insulin secretion deficiency 2
- Fasting insulin levels are similar in obese youth with normal glucose tolerance versus impaired glucose tolerance, potentially missing important diagnoses 2
The Glucose-Ketone Relationship Does Not Reflect Insulin Levels
While the glucose-ketone index has been explored in specific contexts like metabolic therapy for brain cancer 3, this ratio:
- Does not measure or estimate insulin levels—it reflects metabolic state, not insulin concentration
- Ketone production and disposal are influenced by insulin, but the relationship is not linear or predictable enough for clinical estimation 4
- Ketone disposal is reduced in diabetes even when ketone production is normal, suggesting ketone utilization may be more sensitive to insulin deficiency than production 4
When Insulin-Related Testing Is Appropriate
C-peptide measurement (not insulin) has limited but specific clinical utility 1:
- Differentiating type 1 from type 2 diabetes in ambiguous cases (e.g., individuals with type 2 phenotype presenting in ketoacidosis)
- Investigating non-diabetic hypoglycemia to rule out surreptitious insulin administration
- Diagnosing islet cell tumors when inappropriately elevated insulin persists with low glucose
For insulin pump therapy coverage requirements, measure fasting C-peptide when simultaneous fasting plasma glucose is ≤220 mg/dL (12.5 mmol/L) 1.
What Should Be Measured Instead
For diabetes management and monitoring:
- Blood glucose testing via self-monitoring or continuous glucose monitoring 5, 1
- HbA1c for long-term glycemic control assessment 5, 6
- Ketone testing (blood β-hydroxybutyrate preferred over urine) when indicated for DKA risk 1
The bottom line: Insulin levels cannot be reliably determined through glucose-ketone ratios or any other indirect calculation. Direct insulin measurement lacks clinical utility due to assay limitations and biological variability. Focus on glucose monitoring, HbA1c, and clinical assessment for diabetes management decisions.