Normal Insulin Sensitivity — The Healthy Baseline
Modest insulin keeps glucose stable. This is the reference state.
- 70–99: Typical fasting glucose (mg/dL, normal range)
- 2–10: Typical fasting insulin (μIU/mL, low effort)
- < 1.5: Typical HOMA-IR (well within normal)
- 405: Formula constant (mg/dL calibration divisor)
What normal sensitivity looks like
Small insulin pulses. Fast glucose uptake. Low beta-cell workload.
Why the formula works here
Low glucose times low insulin keeps the HOMA-IR ratio small.
Early Insulin Resistance — Tissues Start Responding Less
Cells need more insulin signal to move the same glucose.
- 85–95: Fasting glucose shift (mg/dL, still near-normal)
- 10–15: Fasting insulin rise (μIU/mL, compensating)
- 1.5–2.5: HOMA-IR band (early resistance zone)
- Receptor: Mechanism (signaling blunted downstream)
Subclinical resistance begins
Glucose barely moves; insulin output quietly increases to compensate.
Why this stage is easy to miss
Standard glucose tests look normal; only HOMA-IR flags the drift.
Compensated Insulin Resistance — Hyperinsulinemia Takes Over
Insulin rises substantially while glucose control still holds.
- 90–100: Fasting glucose (mg/dL, near-normal)
- 15–24: Fasting insulin (μIU/mL, compensatory surge)
- 2.5–3.8: HOMA-IR band (compensated resistance zone)
- High: Beta-cell load (sustained hypersecretion)
Compensatory hyperinsulinemia
Pancreas overworks to mask resistance; glucose still looks fine.
A hidden warning sign
Elevated insulin alone often precedes glucose abnormalities by years.
Progressive Beta-Cell Strain — Compensation Starts to Fail
Sustained overwork wears down capacity; glucose begins rising too.
- 100–125: Fasting glucose creep (mg/dL, trending up)
- 24–30: Fasting insulin (μIU/mL, near capacity)
- 3.8–7: HOMA-IR band (progressive strain zone)
- Prediabetes: Trajectory (approaching threshold)
Compensation reaches its limit
Beta cells can no longer fully offset resistance; glucose climbs.
Both markers now moving
Rising glucose plus rising insulin drives HOMA-IR up sharply.
Marked Insulin Resistance — Reading the Final Score
Elevated glucose and insulin together signal significant resistance.
- 125–180: Fasting glucose (mg/dL, elevated)
- 30–40: Fasting insulin (μIU/mL, near-maximal effort)
- > 3.8: HOMA-IR band (marked resistance threshold)
- Diabetes risk: Clinical signal (progression pathway visible)
Interpreting the threshold
HOMA-IR above ~3.8 flags marked resistance in most reference sets.
What happens next clinically
Sustained elevation often precedes prediabetes and type 2 diabetes.