Glucose variability and coefficient of variation
Updated July 3, 2026
Variability describes how much your glucose swings around its average. Two days with the same average can feel very different if one is calm and the other is full of highs and lows. Glynce shows variability two ways, and they answer slightly different questions.
Glucose Variability, the standard deviation
The Glucose Variability card is the standard deviation, or SD, of your CGM readings. It measures the typical distance between a reading and your average, shown in your own glucose unit. A larger number means bigger swings. Because it carries your glucose unit, it tends to rise when your average runs higher, even when the shape of your day is similar.
Coefficient of variation
The Coeff. Var. card is the coefficient of variation, or CV. It divides your standard deviation by your average and shows the result as a percentage, so it stays comparable whether your averages run high or low. International guidance often cites a CV at or below 36 percent as a marker of a more stable pattern for adults with type 1 diabetes. That 36 percent figure is a CV target, not a standard deviation.
Why the two can disagree
Because standard deviation carries your glucose unit and CV adjusts for your average, the two cards can show different labels for the same days. Your standard deviation might read Fair while your CV reads stable, or the reverse. That is expected rather than a fault. CV is the better single number for judging stability, and standard deviation is useful for seeing the raw size of your swings in your own unit.
Why steadier helps
- Fewer large swings usually means fewer lows and fewer sharp highs.
- A steadier pattern is generally easier to plan around.
- Lower variability makes insulin dosing and meal timing more predictable.
Variability is one lens among several. Read it alongside your time in range and average, and focus on your own trend rather than a single threshold.