Glucose-to-Insulin Ratio Calculator
Calculate the fasting glucose-to-insulin (G:I) ratio — a simple low-cost screen for insulin resistance and hyperinsulinemia. A low G:I ratio indicates the pancreas is producing excess insulin to maintain normal glucose. Educational reference only.
⚗️ G:I Ratio Calculator
Glucose-to-Insulin Ratio
(for comparison)
mg/dL
µIU/mL
G:I Ratio Reference Ranges
| G:I Ratio | Interpretation |
|---|---|
| > 12 | Good insulin sensitivity |
| 7 – 12 | Normal range |
| 4.5 – 6.9 | Borderline — possible hyperinsulinemia |
| < 4.5 | Hyperinsulinemia / significant resistance |
Thresholds vary in the literature. Some references use < 7 as the single resistance threshold. The ratio is most useful for detecting hyperinsulinemia before fasting glucose becomes elevated.
Formula
A low G:I ratio means insulin is disproportionately high relative to glucose — a hallmark of hyperinsulinemia and early insulin resistance. The G:I ratio is particularly useful in PCOS and metabolic syndrome screening because it can flag hyperinsulinemia even when fasting glucose is still normal.
Why the glucose-to-insulin ratio is a quick first screen
The fasting glucose-to-insulin ratio does exactly what its name says: it divides your fasting glucose by your fasting insulin. The appeal is its simplicity — there's no special constant or logarithm to apply, just one division you can sanity-check in your head. A low ratio means insulin is high relative to glucose, the classic fingerprint of insulin resistance. A higher ratio points toward better insulin sensitivity.
Because it leans heavily on fasting insulin, the ratio is sensitive to the early phase of insulin resistance, when insulin starts creeping up before glucose has moved at all. That makes it a reasonable first look — though, like every fasting index, it needs a proper 8–12 hour fast to mean anything.
How the ratio is used in PCOS assessment
The glucose-to-insulin ratio earned much of its reputation in the context of polycystic ovary syndrome, where insulin resistance is common even in women who aren't overweight. In that setting a low fasting ratio has been used as a convenient flag for underlying resistance, helping explain symptoms and guiding conversations about management.
Why context matters more than a single cut-off
Proposed thresholds vary, and they shift with age, body weight, and the lab's insulin assay. A value that's reassuring for one person can be borderline for another. The number is most useful as one input — alongside symptoms, weight, family history, and other tests — rather than a stand-alone answer.
Where the glucose-to-insulin ratio falls short
The same simplicity that makes the ratio handy also limits it. It relies entirely on fasting insulin, which varies between labs and from day to day, so a single result can mislead. It hasn't been standardised across populations the way HOMA-IR has, and once someone develops frank diabetes — where the pancreas can no longer over-produce insulin — the ratio loses much of its meaning. For a fuller view, pair it with HOMA-IR or QUICKI, and interpret the result with your provider rather than acting on the number alone.
Frequently Asked Questions
What is a normal glucose-to-insulin ratio?
A fasting glucose-to-insulin ratio above 7 is generally considered normal, and above 12 reflects good insulin sensitivity. A ratio of 4.5–6.9 is borderline, and below 4.5 suggests hyperinsulinemia or significant insulin resistance.
How do you calculate the glucose-to-insulin ratio?
Divide your fasting glucose (mg/dL) by your fasting insulin (µIU/mL). For example, 90 ÷ 10 = 9.0. Both values must come from the same fasting blood draw.
Why is the glucose-to-insulin ratio useful in PCOS?
Because it can flag hyperinsulinemia before fasting glucose rises. In PCOS and metabolic syndrome, insulin is often elevated while glucose still looks normal, and a low G:I ratio detects that pattern.
Is a low or high glucose-to-insulin ratio better?
A higher ratio is better — it means less insulin is needed to maintain normal glucose. A low ratio means insulin is disproportionately high, a sign of insulin resistance.
Sources
- Legro RS et al. "Prevalence and predictors of risk for type 2 diabetes mellitus and impaired glucose tolerance in polycystic ovary syndrome." J Clin Endocrinol Metab. 1999;84(1):165–169.
Last reviewed: June 2025