T1D glossary

Coefficient of variation (CV)

Also called %CV, glycemic variability.

CV measures how much glucose swings, relative to its average: the standard deviation divided by the mean. The 2017 CGM consensus calls glucose stable when CV is under 36%. (International consensus on CGM use, 2017)

Target

36% or lower; some studies suggest under 33% gives extra protection against lows for people who take insulin. (International consensus on time in range, 2019)

Formula

CV (%) = standard deviation of glucose ÷ mean glucose × 100

(Klonoff et al., the Glycemia Risk Index, 2023)

Worked example

Mean 150 mg/dL (8.3 mmol/L) with a standard deviation of 50 mg/dL (2.8 mmol/L): CV = 50 ÷ 150 × 100 = 33%. The same 50 mg/dL standard deviation around a mean of 120 mg/dL gives 42%.

Related terms

• Glycemia Risk Index
• Time below range
• Ambulatory Glucose Profile report

Sources, quoted

• International consensus on CGM use, 2017: “Stable glucose levels are defined as a CV <36%, and unstable glucose levels are defined as CV ≥36%”
• International consensus on time in range, 2019: “Glycemic variability (%CV) target ≤36%”
• International consensus on time in range, 2019: “Some studies suggest that lower %CV targets (<33%) provide additional protection against hypoglycemia for those receiving insulin or sulfonylureas”
• Klonoff et al., the Glycemia Risk Index, 2023: “CV, coefficient of variation (standard deviation of glucose/mean glucose)”

Every quote above is checked against its source page before each update of this site; last checked 2026-10-06. The worked example is our own arithmetic. This page explains a term; it is not advice for a person's treatment.