# Mean amplitude of glycemic excursions (MAGE)

The average size of the day’s larger swings, counting only those bigger than one standard deviation (Service 1970).

Type: cgm_metric · Unit: mmol/L · Domain: Metabolic Health · Accuracy: Calculated · Importance: Context

Also called: glycemic excursions, excursion amplitude, Service MAGE

## In one sentence

The average size of the day's larger swings, counting only the swings bigger than one standard deviation, which is the research literature's classic variability measure and the one most likely to appear in a paper you read.

## Why it exists

It was devised in 1970 at the Mayo Clinic, from blood samples taken every few hours in people with diabetes, as a measure of instability that ignored the small wobbles and counted the real excursions (Service 1970). Fifty years of research used it, which is why VT shows it: when a study reports that something changed MAGE, you can see what the same figure does in your own record. It is less sensitive to small day-to-day noise than the standard deviation and more sensitive to meals.

## What moves it

The same things as the SD, concentrated in the larger swings: meal size and composition, late meals, hard sessions, alcohol nights. A day with one large meal and otherwise flat glucose can have a high MAGE and an ordinary SD.

## How to read it well

Beside the CV, over a period. It has no reference point from healthy-adult sensor studies that VT quotes, and no consensus threshold outside diabetes care, so its use is within your own record.

## How Vitality Tracker uses it

Calculated per day from the valid readings and shown for readers who know it; the period figure is the mean of the days. Not a Vitality Score input.

## How far to trust the number

Calculated; it depends on the day's SD and on the 5-minute resolution of the sensor, so values from VT and from a paper that sampled every hour are not identical quantities.

## Method

For the day, every rise or fall from a trough to a peak (or peak to trough) larger than the day's SD is an excursion; MAGE is the mean of their amplitudes, measured in the direction of the first qualifying excursion (Service 1970).

## Sources

1. Service FJ, Molnar GD, Rosevear JW, Ackerman E, Gatewood LC, Taylor WF. Mean amplitude of glycemic excursions, a measure of diabetic instability. Diabetes 1970;19:644–55. [doi:10.2337/diab.19.9.644](https://doi.org/10.2337/diab.19.9.644).

## Related

- [Standard deviation of glucose](https://vitalitytracker.app/knowledge/glucose-standard-deviation)
- [Coefficient of variation](https://vitalitytracker.app/knowledge/glucose-coefficient-of-variation)
- [Largest amplitude of glycemic excursion](https://vitalitytracker.app/knowledge/lage)
- [Peak rise](https://vitalitytracker.app/knowledge/peak-rise)

Reviewed October 2026 · v1

Source: https://vitalitytracker.app/knowledge/mage