HOMA-IR (Insulin Resistance Index)

What is HOMA-IR (Insulin Resistance Index)?

HOMA-IR is a formula, not a separate blood draw: it combines your fasting glucose and fasting insulin results into one number that research uses as a stand-in for insulin resistance.

HOMA-IR, short for homeostatic model assessment of insulin resistance, is math applied to two numbers you already have: fasting glucose and fasting insulin. Physician-scientist David Matthews and colleagues at Oxford published the original model in 1985 in *Diabetologia*, building it from a simplified model of how the liver and pancreas interact at steady state. The formula, in the units most labs outside the US report, is straightforward: HOMA-IR equals fasting insulin in microU/mL multiplied by fasting glucose in mmol/L, divided by 22.5. When glucose is reported in mg/dL, as it usually is in the US, the working divisor becomes 405 instead (Wallace, Levy, and Matthews, *Diabetes Care*, 2004). That 2004 paper matters for a second reason: it's also where HOMA2 comes from. The original 1985 formula, sometimes called HOMA1, uses simplified approximations. HOMA2 is a nonlinear computer model built two decades later that accounts for variation in liver versus muscle insulin resistance, adjusts for higher glucose readings, and can incorporate C-peptide. Most consumer-facing lab reports and calculators still use the simpler 1985 formula, not HOMA2, so it's worth knowing which version a number came from before comparing it to anything else. Because HOMA-IR is arithmetic performed on two lab values, it isn't a test you order by that name. Your lab report will show a fasting glucose result and a fasting insulin result separately, sometimes with a calculated HOMA-IR value included, sometimes not.

What changed recently

A June 2026 study in *BMC Endocrine Disorders* followed 3,196 adults in the Korean Genome and Epidemiology Study and looked at HOMA-IR alongside body roundness index, a newer measure of central body shape. Adults with both a high HOMA-IR and a high body roundness index had 3.58 times the odds of metabolic dysfunction-associated steatotic liver disease (MASLD) compared with adults low on both, a stronger association than either marker showed alone. MASLD is the name liver societies adopted in 2023, replacing "nonalcoholic fatty liver disease" (AASLD/EASL multi-society consensus, 2023). Separately, a 2026 review in touchREVIEWS in Endocrinology noted that HOMA-IR's dependence on an insulin assay "limits its feasibility in routine practice" compared with tests built only from glucose and triglycerides, the practical reason it shows up less often than simpler surrogates outside research settings.

Tests often checked alongside this

• Fasting glucose — one of the two direct inputs to the HOMA-IR formula itself, not just a related marker.
• Fasting insulin — the other direct input; unlike glucose, insulin immunoassays differ between laboratories, so a HOMA-IR calculated from two different labs' insulin results isn't a clean comparison (Lab Tests Online UK).
• Triglyceride-glucose (TyG) index — a different calculated surrogate using only triglycerides and glucose, no insulin measurement at all, which makes TyG cheaper and easier to standardize since fasting insulin assays are not standardized the way triglyceride and glucose assays are.
• HbA1c — reflects average blood sugar over roughly three months rather than a single fasting moment.
• Lipid panel — often ordered in the same visit when insulin resistance is part of the discussion.

What can affect this marker

• Recent food or drink before the blood draw: insulin and glucose both respond within minutes to eating, so anything other than a true fast pushes the calculated number around.
• Time of day and sleep the night before: insulin sensitivity has a daily rhythm, and shortened sleep has been shown to blunt insulin sensitivity the following morning.
• Acute illness or infection: stress hormones raise blood glucose and insulin output together, temporarily raising a calculated HOMA-IR unrelated to baseline status.
• Which insulin assay the lab used: different immunoassays for insulin can give different absolute numbers on the same sample, a laboratory methods issue rather than a physiological one.
• Body composition and menstrual cycle phase: published cutoff studies note different distributions by BMI category and menopausal status.

What to track over time

• Fasting glucose and fasting insulin values from each visit, ideally noted with the date and which lab ran the insulin assay.
• Whether the sample was a true fasting draw, since a partial fast changes both inputs.
• Any calculated HOMA-IR the lab itself reports on the printed result, alongside the reference range that specific lab used.
• Related results ordered at the same visit, such as HbA1c or a lipid panel.

What to ask your doctor

• What insulin assay does this lab use, and should I try to stick with the same lab if this gets rechecked?
• Which HOMA-IR cutoff, if any, are you using to interpret my result, and why that one for someone like me?
• Would a fasting glucose and HbA1c alone answer the same question, or is the insulin measurement adding something specific here?
• If this comes back elevated, what would the next step be?

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