µIU/mL stands for micro International Units per milli-liter—it’s the standard measurement unit for fasting insulin concentration in blood.

– µ (mu) = micro = one millionth (1/1,000,000)
– IU = International Unit (a standardized measure of hormone activity)
– /mL = per milliliter of blood

So when your lab report shows fasting insulin of 10 µIU/mL, it means there are 10 micro International Units of insulin in every milliliter of your blood.

The Relationship Between HOMA-IR and µIU/mL –  micro-international units per milli-liter

HOMA-IR is calculated from two values:

1. Fasting insulin (measured in µIU/mL)
1. Fasting glucose (measured in mg/dL or mmol/L – milli-moles per litre)

The HOMA-IR Formula:

HOMA-IR = (Fasting Insulin in µIU/mL × Fasting Glucose in mg/dL) ÷ 405

Or if glucose is in mmol/L:

HOMA-IR = (Fasting Insulin in µIU/mL × Fasting Glucose in mmol/L) ÷ 22.5

Examples:

– Excellent metabolic (score of 0.87) could be:
– Fasting insulin: 4 µIU/mL
– Fasting glucose: 88 mg/dL
– HOMA-IR = (4 × 88) ÷ 405 = 0.87
– Moderate insulin resistance (HOMA-IR of 4):
– Fasting insulin: 15 µIU/mL
– Fasting glucose: 108 mg/dL
– HOMA-IR = (15 × 108) ÷ 405 = 4.0
– Severe insulin resistance (HOMA-IR of 6):
– Fasting insulin: 22 µIU/mL
– Fasting glucose: 110 mg/dL
– HOMA-IR = (22 × 110) ÷ 405 = 6.0

Key Insight:

The µIU/mL measurement tells you the absolute amount of insulin your pancreas is producing while fasting. HOMA-IR tells you how effectively that insulin is working to control glucose.

High insulin (high µIU/mL) combined with normal or elevated glucose creates a high HOMA-IR score—revealing that your cells are resistant to insulin’s signals, forcing your pancreas to overproduce insulin to maintain blood sugar control.

This is why someone can have “normal” fasting glucose (under 100 mg/dL) but still have severe metabolic dysfunction if their fasting insulin is elevated above 10-12 µIU/mL.