In one sentence
The day's highest reading minus its lowest: the size of the biggest swing, one number per day, with nothing to work out.
Why it matters
It is the easiest variability figure to picture and the one most people check first: how far apart were my best and worst moments today? A day with a LAGE of 3 mmol/L had a quiet range; a day with 6 had a large meal or a hard session in it, or both. It is also the most fragile figure on the shelf, because one false reading at either end sets it.
What moves it
The single biggest meal or the single hardest session of the day sets the top; the night, or a long gap between meals, sets the bottom. A compression low at 3 a.m. can double it, which is why VT takes flagged readings out before it is computed.
How to read it well
As a daily companion to the meal log: the day's LAGE and the meal that caused it. For a period, read the median of the daily values rather than their maximum.
How Vitality Tracker uses it
Calculated per day from valid readings; the period figure is the median of the days. Not a Vitality Score input.
How far to trust the number
Calculated from two measured readings, the two most likely to be wrong; the artifact filter does most of the work of making it trustworthy.
Sources
- Vitality Tracker, Knowledge Base brief, catalogue D; the definition is arithmetic and has no primary source beyond common use in the CGM literature.