How this instrument works
QUICKI stands for quantitative insulin sensitivity check index. Take the base-10 logarithm of fasting insulin in µU/mL, add the base-10 logarithm of fasting glucose in mg/dL, and divide 1 by that sum. Logarithms compress a wide range into a narrower, more even one, which is the whole point: raw insulin and glucose values can span an order of magnitude between a lean, sensitive person and a resistant one, and a straight product exaggerates that spread. Katz and colleagues, publishing in the Journal of Clinical Endocrinology & Metabolism in 2000, built QUICKI specifically to correlate more evenly with the hyperinsulinemic-euglycemic clamp — still the reference method — across nonobese, obese, and diabetic volunteers alike.
This site also carries HOMA-IR, which uses the identical pair of fasting values but multiplies them together and divides by 405. The two indices run in opposite directions, and mixing that up is an easy mistake: a higher QUICKI points toward better sensitivity, while a higher HOMA-IR points toward more resistance. Katz's team found their logarithmic version tracked the clamp technique more consistently than the simple product across a broader spread of subjects, from lean volunteers to people with established type 2 diabetes. Neither figure replaces the other — clinics and researchers often report both from the same draw, since they draw on identical inputs and cost nothing extra to compute.
Typical QUICKI values sit somewhere between about 0.30 and 0.45 in healthy, sensitive adults, drifting down toward 0.30 or below as resistance sets in — though, as with HOMA-IR, no single line in the sand separates normal from abnormal, and thresholds shift somewhat by lab and population studied. Treat one reading as a data point to track alongside fasting glucose and A1C rather than a standalone verdict, and remember the formula assumes a genuine fasting state; a missed fast shifts both inputs enough to move the result meaningfully.
- Draw both values from a true fasting panel — at least 8 hours with nothing but water beforehand.
- Enter Fasting insulin in µU/mL.
- Enter Fasting glucose in mg/dL.
- Read QUICKI; higher means more insulin-sensitive, the opposite direction from this site's HOMA-IR calculator.
Worked example — three fasting panels
Fasting insulin 10 µU/mL, fasting glucose 90 mg/dL: log₁₀(10) = 1.0000, log₁₀(90) = 1.9542, summing to 2.9542. Divide 1 by that and QUICKI comes out to 0.3385 — squarely in the range read as insulin-sensitive.
Push insulin to 25 µU/mL and glucose to 126 mg/dL, the threshold used for a standalone diabetes diagnosis: log₁₀(25) = 1.3979, log₁₀(126) = 2.1004, summing to 3.4983. One divided by that gives 0.2859 — lower, consistent with insulin resistance, and worth noticing that it moved in the opposite direction a rising HOMA-IR would.
A leaner pairing — insulin 5 µU/mL, glucose 85 mg/dL — gives log₁₀(5) = 0.6990 and log₁₀(85) = 1.9294, summing to 2.6284. One divided by that is 0.3805, at the higher, more sensitive end of the three readings.
Questions
Why does QUICKI use logarithms instead of just multiplying, like HOMA-IR does?
Because Katz and colleagues found that a straight product exaggerates the spread between very sensitive and very resistant people, while the logarithmic version tracked the hyperinsulinemic-euglycemic clamp — the reference method neither index can replace — more consistently across nonobese, obese, and diabetic subjects in their original 2000 validation. Both formulas use the same fasting insulin and glucose pair; QUICKI just combines them differently.
Why does a higher QUICKI mean something different from a higher HOMA-IR?
Because the two indices measure the same underlying biology from opposite ends. HOMA-IR rises as resistance worsens, so a bigger number is the worse sign. QUICKI is built as 1 divided by a sum, so it falls as resistance worsens — a bigger number here is the better sign. Reading one scale with the other's intuition is the single most common mix-up between the two.
What counts as a normal QUICKI value?
Most healthy, sensitive adults land somewhere between about 0.30 and 0.45, with figures below roughly 0.30 more often seen alongside resistance or type 2 diabetes. There's no single agreed cutoff — thresholds shift with the population studied and the assay a given lab runs — so treat the number as one input into a broader metabolic picture rather than a pass-or-fail line.
Can I calculate both QUICKI and HOMA-IR from the same blood draw?
Yes — both formulas need nothing more than fasting insulin and fasting glucose, so a single draw feeds either calculator, or both. Researchers frequently report both figures side by side precisely because they cost nothing extra once the panel is drawn, even though they rarely disagree about the overall direction, sensitive versus resistant.
Does fasting length actually change the result?
Considerably. The formula assumes a genuine fast, generally 8 to 12 hours with only water permitted. Eating, sweetened coffee, or even caffeine's mild effect on insulin shortly before the draw can shift glucose and insulin enough to move the index meaningfully — exactly why labs enforce a strict fasting window before drawing either value.
Can QUICKI diagnose diabetes or PCOS on its own?
No. It's a research and screening tool, not a diagnostic criterion. Diabetes is confirmed through fasting glucose, A1C, or an oral glucose tolerance test, and PCOS relies on the Rotterdam criteria; resistance shows up often alongside both, which is why QUICKI gets measured in that context, but one reading without supporting findings isn't a diagnosis by itself.
References
- Katz A, Nambi SS, Mather K, et al. 2000, J Clin Endocrinol Metab — original QUICKI validation (PubMed)
- NIDDK — Insulin Resistance & Prediabetes
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.