Understanding Glucose Spikes

For a complete overview of all Levels scores and metrics, see How Levels Scores and Glucose Metrics Work: A Complete Guide.

A "spike" is a casual term for a sharp rise in glucose. It has no clinical definition.

How Levels defines a spike

The Levels app labels a spike when both of the following are true:

Your glucose exceeds 109 mg/dL.
The rise from your baseline to the peak is +30 mg/dL or more.

Both conditions must be met. If your glucose rises 30 points but stays below 109, it is not labeled a spike. If your glucose goes above 109 but the rise from baseline is less than 30, it is also not labeled a spike.

For example, if your baseline glucose is 95 mg/dL and your peak is 130 mg/dL, that would be labeled a spike (+35 rise, above 109). If your glucose goes from 100 mg/dL to 125 mg/dL, that would not be labeled a spike (only a +25 rise).

How baseline glucose is calculated

Baseline is the reference point Levels uses to measure how much your glucose has risen. Understanding how it works is key to understanding your spike values.

Your baseline is a rolling average of your glucose readings over the previous four hours.
It is personalized to your data and updates continuously as new readings come in.
It is not the lowest visible point on your glucose graph. It is a computed average, which means it may be higher or lower than any single point you can see on the chart.

Why the spike number may not match your math

This is one of the most common sources of confusion. If you subtract the lowest visible point on the graph from the peak, the result will likely differ from the spike value shown in the app. Here is why:

The spike value (the +X number) is calculated as peak minus your four-hour rolling baseline average, not peak minus the lowest visible point on the graph.
For example, if the app shows a +35 spike and your peak was 112 mg/dL, that means your computed baseline at that moment was approximately 77 mg/dL (112 minus 35). Even if the lowest point you see on the graph is 85, the four-hour rolling average was lower than that single reading.
You cannot reverse-engineer the spike value by eyeballing two points on the graph. The baseline is an invisible computed value, not a single data point.

What the +X spike value means

When you see a number like +35 on your glucose graph, that is the difference between your four-hour rolling baseline and the peak of the spike. A larger number means a bigger rise from your recent trend. A smaller number (closer to +30) means the rise just barely crossed the spike threshold.

Spike phases

When a spike is detected, the app tracks its progression through several phases:

Spiking: Your glucose has exceeded +30 mg/dL above your baseline. The spike is active and may still be rising.
Recovering: Your glucose has crossed back below the spike threshold and stayed there within a one-hour window. Your body is clearing the excess glucose.
Crashing: Your glucose has dropped 10 points below the pre-spike baseline within 30 minutes of crossing below the spike threshold. This can sometimes cause feelings of shakiness, hunger, or fatigue.

What does a spike mean?

The shape of your glucose curve matters. In general, we look at three components when analyzing a spike:

Glucose increase: the absolute change between baseline and peak
Glucose slope: how quickly your glucose rose
Area under the curve: how long your glucose stayed elevated before returning to baseline

A spike does not necessarily indicate an issue. Given a large enough carbohydrate load, most people will see a spike.

What can be more telling is how high your glucose goes and how long it stays elevated. An optimal response typically returns to baseline within 90 to 120 minutes.

A slower return may reflect reduced insulin sensitivity (insulin resistance), which can be a precursor to pre-diabetes and type 2 diabetes.

What should I do about a spike?

Metabolic health is about long-term trends, not single incidents. Many factors can affect your glucose response day to day, including poor sleep, recent exercise, elevated glucose from a previous meal, stress, time of day, and overall health.

When interpreting glucose rises, consider:

The shape of your curves and how often you see sharp rises that take a long time to return to baseline
Which foods tend to cause spikes (including refined flours and "hidden" sugars)
Lifestyle context like sleep and stress
Your overall health

Learn more

Gentle reminder: Levels is a general health and wellness app. If you have questions or concerns about your individual metabolic health data, please speak to your doctor.