How this calculator works
Katz and colleagues defined QUICKI using base-10 logs of fasting insulin and glucose in specified units. It is a surrogate research index of insulin sensitivity. The inverse modes are algebraic exercises, not glucose or insulin targets. This page uses the conventional rounded glucose factor 18 and does not convert insulin assays from pmol/L. The result is an estimate for information only and is not medical advice.
Formula
QUICKI = 1/[log10(I) + log10(G)], with I in microIU/mL and G in mg/dL. G = 10^(1/QUICKI - log10(I)); I = 10^(1/QUICKI - log10(G)).
Worked example
With fasting insulin 10 and glucose 100 mg/dL, the denominator is 1 + 2 = 3, so QUICKI is 1/3. Insulin 1 with glucose 100 gives 1/2.
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Frequently asked questions
Why base-10 logarithms?
They are part of the published index. Natural logarithms would change its scale.
Can this diagnose insulin resistance?
No. Assay and population differences matter, and interpretation requires clinical context.
Why can very small inputs be rejected?
The log sum must be positive for the positive QUICKI scale used here. A zero denominator or overflow cannot produce a valid result.