What is the normal range for Homeostatic Model Assessment for Insulin Resistance (HOMA-IR)?

Normal Range of HOMA-IR for Insulin Resistance Assessment

The normal reference interval for HOMA-IR is between 0.4 and 2.4, with values ≥2.5 considered a reasonable indicator of insulin resistance. 1

Understanding HOMA-IR

HOMA-IR (Homeostatic Model Assessment for Insulin Resistance) is a validated surrogate measure of insulin resistance calculated using the formula:

• HOMA-IR = [fasting serum glucose (mmol/L) × fasting serum insulin (mU/ml)] / 22.5

Lower values indicate greater insulin sensitivity, while higher values suggest insulin resistance.

Clinical Applications

HOMA-IR provides several clinical benefits:

• Serves as an acceptable alternative to more expensive and time-consuming dynamic testing for insulin resistance 2
• Helps identify patients at risk of NASH (non-alcoholic steatohepatitis) or fibrosis progression in selected cases 2
• Can monitor improvements in insulin sensitivity during weight loss interventions 2, 3

Reference Intervals and Interpretation

Reference intervals for HOMA-IR have been established through rigorous research:

• Normal range: 0.4-2.4 based on studies following Clinical and Laboratory Standards Institute guidelines 1
• Values ≥2.5 should be considered indicative of insulin resistance 1
• Population-based studies have found median HOMA-IR values of:
  • 1.09 (IQR 0.85-1.42) in healthy individuals 4
  • 1.54 (IQR 1.13-2.19) in non-diabetic individuals 4
  • 2.00 (IQR 1.39-2.99) in prediabetic individuals 4
  • 4.00 (IQR 2.52-6.51) in diabetic individuals 4

Important Considerations and Limitations

When using HOMA-IR in clinical practice, consider these important caveats:

1. Assay variability: HOMA-IR values depend on the insulin assay used, requiring assay-specific reference intervals 4

2. Limited utility in diabetes: The validity of HOMA-IR depends on the ability of insulin secretion to adapt to insulin resistance, questioning its suitability in overt diabetes 2

3. Lack of standardized threshold: There is no universal agreement on a threshold defining insulin resistance using HOMA-IR 2

4. Clinical context matters: HOMA-IR is of limited use for NAFLD diagnosis in patients with metabolic risk factors but can confirm altered insulin sensitivity in cases of diagnostic uncertainty 2

5. Reference values are essential: HOMA-IR should only be used when proper reference values have been established 2

Clinical Applications in Monitoring

HOMA-IR can effectively monitor metabolic improvements during lifestyle interventions:

• Studies show HOMA-IR decreases in an over-proportional manner (45% reduction) compared to BMI reduction (10%) during lifestyle modification programs 3
• Improvement in HOMA-IR during weight loss may indicate metabolic improvement beneficial for conditions like NAFLD 2
• HOMA-IR shows high inter-individual variation, allowing personalized monitoring of insulin sensitivity improvements 3

Alternative Insulin Resistance Measures

For comparison, other insulin resistance measures include:

• 1/HOMA-IR: The reciprocal index shows comparable correlation with clamp-derived insulin resistance measures 5
• QUICKI (Quantitative Insulin Sensitivity Check Index): Shows strong correlation with clamp-derived measures similar to HOMA-IR 5
• LP-IR (Lipoprotein Insulin Resistance Index): A newer measure based on NMR-derived lipoprotein information that shows stronger associations with HOMA-IR and glucose disposal rates than traditional measures 6

In summary, while HOMA-IR provides a valuable clinical tool for assessing insulin resistance with a normal range of 0.4-2.4, its interpretation should consider the specific insulin assay used and the clinical context of each patient.