How to read your own glucose curve

The overnight baseline

The flattest, most comparable part of your trace is the small hours, when you are neither eating nor moving. It is the closest thing a sensor gives you to a fasting glucose, measured repeatedly instead of once.

It is also the part least distorted by the day's noise, which makes a drift upward across several weeks more meaningful than any individual meal.

Peaks, and how much to make of them

A meal peak has three properties worth reading: how high it goes, how long it stays up, and how cleanly it returns. The return is the part most people ignore and the part that carries the most information — a peak that comes down promptly is a different signal from the same peak that lingers for three hours.

The important corrective is that spiking is not itself abnormal. When researchers put sensors on people who are normoglycaemic by standard tests, those people spent a meaningful share of their time in ranges usually described as prediabetic. If you wear a sensor expecting a flat line, you will find something alarming, because a flat line is not what a working metabolism produces.

Ce que disent les preuves

• People classified as normoglycaemic by standard tests still spent about 15% of monitored time in the prediabetic glucose range and 2% in the diabetic range.¹

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• Where glucose spikes are linked to harm, the evidence points to frequent, sustained spikes over time rather than isolated ones, and popular sources claim effects the medical literature does not support.²

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Your curve is yours

Two people eating the same meal can produce clearly different responses. In a cohort of 800 people whose responses to nearly 47,000 meals were recorded, variability between individuals given identical food was high enough that universal advice about which foods spike people has limited value.

This is the strongest argument for personal measurement, and it is worth stating carefully: the finding is that responses differ, not that acting on your own differences has been shown to improve long-term health.

Ce que disent les preuves

• Responses to identical meals vary substantially between individuals, which limits how far general glycaemic advice transfers to any one person.³

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What the sensor you chose can actually show

Shape needs sampling. A sensor reporting every fifteen minutes may place three or four points across a rise-and-fall that a one-minute sensor draws with sixty. The peak can be blunted or missed outright.

This matters most for exactly the readers told they should care about shape — the food-and-exercise testers. Several of the sensors marketed for that purpose are among the slowest-reading on the market.