Insulin Resistance: Looking Beyond Normal Blood Sugar
Many people mistakenly think: normal blood sugar means no insulin resistance.
In the early stages of insulin resistance, the body may produce more insulin to temporarily keep blood glucose within the normal range, so fasting blood glucose and HbA1c may still be normal. [1]
Two indicators can provide additional information, but neither can diagnose or rule out insulin resistance on its own.
1. Fasting insulin and fasting blood glucose
These measurements can be used to estimate HOMA-IR:
HOMA-IR = fasting insulin (μU/mL) × fasting blood glucose (mmol/L) ÷ 22.5 [2]
A higher value usually indicates lower insulin sensitivity. This formula requires the units shown above; glucose reported in mg/dL must not be inserted into the formula with a divisor of 22.5.
HOMA-IR is an estimate, not a stand-alone diagnosis. Results depend on the laboratory method and the population being assessed, and there is no single cutoff suitable for everyone. Tests for insulin resistance are used mainly in research and are not routine screening tests that everyone needs. A clinician can assess whether testing is useful in your situation. [1]
2. Waist-to-height ratio
Waist-to-height ratio = waist circumference ÷ height
Use the same units for both measurements. A simple message for many adults is to keep the waist circumference below half the height. For example, for a person who is 170 cm tall, this corresponds to a waist circumference below 85 cm. [3]
Waist-to-height ratio is an indicator of central obesity and related metabolic risk; it does not directly measure visceral fat or diagnose insulin resistance. NICE recommends using it alongside BMI in adults with a BMI below 35 kg/m². It is not intended for use during pregnancy. [3]
Look at the whole picture
Normal blood sugar does not necessarily exclude insulin resistance. Equally, HOMA-IR and waist-to-height ratio should not be used alone to confirm or exclude it. Results need to be considered alongside medical history, other risk factors and a healthcare professional’s assessment.
This article provides general information and does not replace medical assessment, diagnosis or treatment.