HOMA-IR
A single number quantifying insulin resistance — calculated from two fasting blood tests
HOMA-IR combines your fasting glucose and fasting insulin into one insulin resistance score. It detects metabolic dysfunction years before diabetes appears on glucose testing alone — and it's the most widely used clinical measure of insulin sensitivity.
The Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), developed by Matthews et al. in 1985, estimates insulin sensitivity from fasting steady-state insulin and glucose levels. The principle: higher insulin needed to maintain a given glucose = more resistance. At fasting steady state, the glucose-insulin relationship is predictable — deviation from the expected ratio quantifies insulin resistance.
Reference Ranges
How clinicians interpret HOMA-IR results — from optimal to concerning.
⚠ Reference ranges vary by laboratory and assay. Always interpret your result in context of your laboratory's own reference intervals and your clinical presentation.
What raises HOMA-IR
Visceral adipose tissue releases FFAs and adipokines that impair insulin signalling in liver and muscle.
Sedentary behaviour reduces GLUT4 expression in skeletal muscle — the primary glucose uptake pathway.
Even one night of sleep deprivation elevates cortisol and causes insulin resistance comparable to months of sedentary behaviour.
Frequent glucose/fructose spikes chronically stimulate insulin secretion, driving receptor downregulation over time.
Glucocorticoids increase hepatic gluconeogenesis and peripheral insulin resistance — HOMA-IR rises within days of starting steroids.
What lowers HOMA-IR
GLUT4 upregulation in muscle persists 24–72h post-session. Regular exercise lowers HOMA-IR by 30–50% in insulin-resistant adults.
Even modest weight loss dramatically reduces hepatic fat — HOMA-IR falls more than proportionally to weight lost.
High olive oil, vegetables, fish, low refined carbohydrate — reduces HOMA-IR by 20–30% independent of weight loss.
Reduces hepatic gluconeogenesis and improves hepatic insulin sensitivity — lowers HOMA-IR as first-line IR pharmacotherapy.
Treating OSA with CPAP reduces HOMA-IR — sleep quality directly impacts insulin sensitivity through cortisol and GH regulation.
Conditions this biomarker signals
When HOMA-IR is outside normal range, these are the most clinically significant possibilities.
HOMA-IR ≥ 2.5 correlates with waist circumference, triglycerides, blood pressure, and low HDL — a proposed composite criterion.
HOMA-IR ≥ 2.0 in PCOS predicts need for metformin and severity of hyperandrogenism — key treatment decision point.
Stronger predictor of NAFLD than BMI alone — elevated HOMA-IR with raised ALT suggests early NASH progression.
HOMA-IR > 3 with IFG doubles T2DM progression rate — identifies the highest-need group for aggressive prevention.
Which tests measure this biomarker
HOMA-IR may be included in or ordered alongside these panels.
HOMA-IR = (insulin × glucose) ÷ 22.5 for mmol/L; ÷ 405 for mg/dL. Some labs report directly.
The maths behind HOMA-IR: modelling the insulin-glucose feedback loop
HOMA-IR is derived from a mathematical model of glucose-insulin homeostasis. At fasting steady-state, blood glucose is determined by the balance between hepatic glucose output (opposed by insulin) and peripheral glucose disposal (insulin-dependent). If insulin sensitivity halves, twice as much insulin is needed to maintain the same glucose — HOMA-IR doubles. The "22.5 constant" is derived from the reference state: a normally insulin-sensitive individual with fasting insulin of 5 µIU/mL and glucose of 4.5 mmol/L, giving HOMA-IR = 1.0. The same model also produces HOMA-β (beta-cell function), allowing tracking of both IR and beta-cell exhaustion simultaneously.
HOMA developed in 1985, still gold standard
Published by Matthews et al. in Diabetologia in 1985. Despite 40 years of newer tests, HOMA-IR remains the most widely used clinical and research insulin resistance measure. The euglycaemic hyperinsulinaemic clamp remains the definitive reference standard but requires IV infusion and 3-hour hospital procedure — HOMA-IR provides ~85% of the clinical information from two fasting blood draws.
The "22.5 constant" derives from a normal reference
The denominator 22.5 is the product of fasting insulin (5 µIU/mL) × fasting glucose (4.5 mmol/L) expected in a normally insulin-sensitive individual, giving HOMA-IR = 1.0. The formula is dimensionally consistent for mmol/L glucose — for mg/dL, the denominator changes to 405. Units matter.
HOMA also estimates beta-cell function
HOMA-β = (20 × fasting insulin) ÷ (fasting glucose − 3.5) × 100%. HOMA-β above 100% indicates compensatory hypersecretion; falling HOMA-β with rising HOMA-IR tracks the progression from insulin resistance to overt T2DM — the two hallmarks of metabolic deterioration.
Clinical use — when and why this is ordered
How clinicians use HOMA-IR in practice — the real-world scenarios where it changes decisions.
Metabolic risk stratification beyond glucose
Identifies insulin-resistant patients with normal fasting glucose — the 10–15 year preventive window. Triggers intensive lifestyle intervention before T2DM develops.
PCOS management
HOMA-IR ≥ 2.0 supports metformin initiation in PCOS. Serial HOMA-IR tracks response to lifestyle + pharmacotherapy.
NAFLD severity assessment
Combined with liver enzymes and FIB-4 score — HOMA-IR > 3.0 predicts more severe hepatic steatosis and fibrosis progression risk.
Research and clinical trial enrolment
HOMA-IR is the most widely reported insulin resistance metric in clinical research — used to select and stratify insulin-resistant participants.