METS-IR

METS-IR (Metabolic Score for Insulin Resistance) is a calculated index that estimates how insulin-resistant a person is using four routine measurements — fasting glucose, fasting triglycerides, HDL cholesterol and body mass index — without measuring insulin at all. It exists because the direct methods are impractical: the reference method, the euglycemic-hyperinsulinemic clamp, is a research procedure, and fasting insulin assays are poorly standardized between labs. METS-IR was developed and validated against clamp-derived insulin sensitivity as a cheap stand-in that any standard fasting panel already contains. It is a screening and research score, not a diagnosis.

What it measures

The index is a formula, not a test. It is calculated as the natural logarithm of (2 x fasting glucose + fasting triglycerides), multiplied by BMI, divided by the natural logarithm of HDL cholesterol. Every input comes from one fasting blood draw plus your height and weight. What it captures is the pattern that insulin resistance produces: glucose drifting up, triglycerides rising, HDL falling, body mass increasing. It never observes insulin action directly, so it is a proxy for the biology rather than a reading of it — the deeper reference, including how it compares with insulin-based scores, is the METS-IR entry at Smart Longevity.

Typical values

METS-IR is a dimensionless number with no units. Higher means more insulin resistance. There is no single universal reference range: the thresholds published for it come from specific cohorts and shift with population, age, sex and body composition, and many studies avoid a fixed cut-off entirely and instead compare people by quartile of the score. Treat your own number as a position on a scale and as something to track over time, not as a pass or fail line.

Units matter more than people expect. The formula is written for glucose, Triglycerides and HDL in mg/dL. If your lab reports in mmol/L, convert first, and note that the conversion factor is not the same for glucose as it is for the two lipids. A calculator fed the wrong units returns a number that looks plausible and is meaningless.

Why it matters for longevity

Reduced sensitivity to insulin sits upstream of much of what shortens healthspan — type 2 diabetes, high blood pressure, fatty liver disease and atherosclerotic cardiovascular disease — and Insulin resistance is usually present for years before fasting glucose crosses any diagnostic threshold. In observational cohorts, a higher METS-IR is associated with a higher risk of developing those conditions, and the association generally survives adjustment for the usual confounders. That evidence is associational. No trial has shown that lowering the score itself changes outcomes; the score is a marker of a trajectory, and its value is that it flags the trajectory early and from data most people already have.

What changes it

Because METS-IR is built from four modifiable inputs, the things that move it are the ordinary metabolic levers. Losing fat mass lowers BMI and usually pulls triglycerides down with it. Cutting refined carbohydrate and alcohol lowers triglycerides quickly, often within weeks. Regular aerobic work plus resistance training improves glucose disposal and adds muscle, and short walks after meals blunt the glucose spikes that feed the fasting number. Sleep debt and chronic stress push fasting glucose the other way. Several drugs — metformin, GLP-1 receptor agonists, fibrates — change components of the score directly.

Two cautions. HDL is the least responsive input to lifestyle change, so do not judge progress by it alone. And because BMI multiplies the whole expression, a very muscular person can score high without being insulin-resistant, which is one reason the index reads better as a screen for a population than as a verdict on an individual.

Related reading

Disclaimer. This article is for information only and does not replace medical advice. Talk to a qualified clinician before changing anything about your health.