Glucose Variability (CV and SD)

Glucose variability measures how much your blood sugar fluctuates up and down. Two readings could have the same average but very different variability — and high variability is independently linked to diabetes complications, even when average glucose looks acceptable.

How It Works

The app calculates two related measures:

Standard Deviation (SD): The average distance each reading is from your mean glucose. Measured in mg/dL. An SD of 15 means your readings typically swing about 15 mg/dL above and below your average.

Coefficient of Variation (CV): SD expressed as a percentage of your mean, so you can compare variability across different average glucose levels.

CV = (SD ÷ Mean glucose) × 100%

For example: SD of 20, mean of 110 mg/dL → CV = (20 ÷ 110) × 100 = 18.2%

Your Target

• Below 25% — Excellent stability. Your glucose is predictable and well-controlled.
• 25–30% — Good. Minor adjustments to diet or timing may help.
• 30–36% — Moderate variability. Worth identifying triggers (specific foods, sleep, stress).
• Above 36% — High variability. This level warrants a conversation with your doctor.

For SD: a value below 25 mg/dL is generally considered stable for people with prediabetes.

Why This Matters

Research shows that high glucose variability is an independent risk factor for cardiovascular complications and oxidative stress — even when average glucose is normal. Swinging between highs and lows is harder on your blood vessels than a steady, slightly elevated level. CV is considered a more reliable variability measure than SD alone because it accounts for differences in baseline glucose levels.

What You Can Do

• Identify which meals or days produce the widest swings and compare them to your calmer days.
• Common causes of high variability: skipping meals, very high-carbohydrate meals followed by long gaps, irregular sleep, or high stress.
• Eating at consistent times each day is one of the most effective ways to reduce CV.
• Pairing carbohydrates with protein, fat, and fiber buffers the rise and fall, smoothing out variability.

Based on: Rodbard D., Diabetes Technology & Therapeutics 2011; Danne et al., International Consensus 2019