Matsuda Index Calculator
Matsuda Index Calculator
Estimate whole-body insulin sensitivity from a standard 75 g oral glucose tolerance test, combining fasting and mean post-load glucose and insulin.
Matsuda Index
OGTT-derived indexFasting glucose 95 mg/dL, fasting insulin 12 µU/mL, mean OGTT glucose 160 mg/dL, mean OGTT insulin 65 µU/mL
Formula
- G₀, I₀
- fasting plasma glucose (mg/dL) and fasting insulin (µU/mL)
- Ḡ, Ī
- mean glucose and mean insulin across all OGTT timepoints — typically 0, 30, 60, 90 and 120 minutes of a 75 g load
- 10,000
- a scaling constant chosen so scores fall in a convenient range; it has no physiological meaning
- direction
- unlike HOMA-IR, a higher Matsuda score means better insulin sensitivity, not worse
Worked example
Fasting glucose 95 mg/dL, fasting insulin 12 µU/mL, mean OGTT glucose 160 mg/dL, mean OGTT insulin 65 µU/mL
95 × 12 × 160 × 65 = 11,856,000
√11,856,000 = 3,443.25
10,000 ÷ 3,443.25 = 2.90
Matsuda index bands
| Score | Interpretation |
|---|---|
| Below 2.5 | Insulin resistant |
| 2.5 – 5.0 | Intermediate |
| Above 5.0 | Insulin sensitive |
What the mean OGTT values represent, and why Matsuda differs from HOMA-IR
The Matsuda index needs a full 75 g oral glucose tolerance test, not a single fasting sample. Ḡ and Ī are the arithmetic mean of glucose and insulin measured at every timepoint of the test — conventionally 0, 30, 60, 90 and 120 minutes, though some protocols use only 0, 60 and 120. Averaging across the curve, rather than using any single value, is what gives the index its stability against a transient spike or dip at one draw.
The distinction from HOMA-IR is mechanistic, not just procedural. HOMA-IR is derived entirely from fasting values and reflects hepatic insulin sensitivity — how well insulin suppresses glucose output from the liver in the basal state. Matsuda incorporates the post-load response and correlates more closely with whole-body sensitivity, dominated by skeletal muscle glucose uptake, which is where most insulin-stimulated glucose disposal actually happens. The two indices can disagree in a given patient, and that disagreement is itself informative about where resistance is concentrated.
As with every surrogate index, the cut-offs are not fixed physical constants. They were derived against euglycaemic clamp data in specific study populations, and both the assay used for insulin and the ethnicity and body composition of the cohort shift the numbers that separate resistant from sensitive. 2.5 is the figure most commonly quoted, but treat it as a starting point rather than a diagnostic threshold.
Frequently asked questions
What are the OGTT mean values in the Matsuda formula?
The arithmetic mean of glucose and insulin across all timepoints of a standard 75 g oral glucose tolerance test — typically 0, 30, 60, 90 and 120 minutes.
How does the Matsuda index differ from HOMA-IR?
HOMA-IR uses only fasting glucose and insulin and reflects hepatic insulin sensitivity. Matsuda incorporates the post-load OGTT response and better reflects whole-body sensitivity, including skeletal muscle.
What counts as insulin resistant on the Matsuda index?
A score below 2.5 is the most commonly quoted cut-off for insulin resistance, though this varies between populations and insulin assays and is not a universal threshold.
Can Matsuda be calculated from a shortened OGTT?
Some protocols use only three timepoints (0, 60, 120 minutes) instead of five. This changes the mean values slightly, so results from different protocols are not perfectly interchangeable.
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References
- Matsuda M, DeFronzo RA. Insulin sensitivity indices obtained from oral glucose tolerance testing: comparison with the euglycemic insulin clamp. Diabetes Care. 1999;22(9):1462–70.
- DeFronzo RA, Tripathy D. Skeletal muscle insulin resistance is the primary defect in type 2 diabetes. Diabetes Care. 2009;32(Suppl 2):S157–63.