How Do I Find My Biggest Glucose Spikes in a Month of CGM Data?
Your biggest CGM spikes are the largest rises from pre-meal baseline to peak, not the highest absolute readings. The free HealthOS report ranks them.
Your biggest glucose spikes in a month of CGM data are not your highest glucose readings. They are the largest rises from the flat baseline before a meal to the peak after it. Drop a LibreView, Dexcom Clarity, Stelo, Lingo, SiBionics or Apple Health export into HealthOS's free browser report at https://healthosx.com/glucose and it ranks those rises for you, no scrolling day by day, no account.
How do I find my biggest glucose spikes in a month of CGM data?
Get the export from your sensor's app first. On a computer, LibreView lets you download a glucose CSV. Dexcom Clarity, Stelo, Lingo, SiBionics and Apple Health all have export options too. Then:
- Go to https://healthosx.com/glucose
- Drop the file there. It stays in your browser and nothing is uploaded.
- Open the Biggest rises section. The report sorts excursions by the size of the rise, not by the peak glucose reading.
- Note the time and the size, then check anything close to a meal.
Illustrative. The top few rises are the ones to inspect first.
The largest rise is not your highest glucose reading. It is the biggest change from the flat point before the meal to the peak after it.
A spike is a rise, not a high reading
Two people can both touch 160 mg/dL after eating. One started at 90 and rose 70 mg/dL. The other started at 130 and rose 30 mg/dL. The first is a much larger post-meal response, even though the peak number is identical. If you scroll a raw CGM trace, your eye sees the 160 and misses the baseline underneath it.
| Person A | Person B | |
|---|---|---|
| Pre-meal baseline | 90 mg/dL | 130 mg/dL |
| Post-meal peak | 160 mg/dL | 160 mg/dL |
| Actual rise | 70 mg/dL | 30 mg/dL |
Scroll the table sideways for the rest →
Illustrative. The rise is the change from the pre-meal baseline to the peak, not the peak itself.
That is why a useful spike report starts from the stable reading before the slope. It looks for a flat stretch, follows the climb to the highest point before the fall, and reports the difference. A rise of 70 mg/dL from a low baseline and a rise of 20 mg/dL from a high baseline are different events, even if the second person ends at a higher absolute value.
Why a month of data hides the biggest rises
One month is thousands of readings. The largest post-meal rise is not always on your worst-looking day. It may happen on a day when your baseline was low, after a meal you thought was safe, and the peak did not look dramatic because the absolute number stayed under 150. The shape matters more than the top number: flat baseline, steep upslope, early peak, return.
CGM sensors also sample every few minutes. A fast spike can peak between two readings, so the sensor records a lower value than your true peak. The biggest rises section is still the best first pass, but treat any single number as an estimate, not a lab result.
What the report can and cannot conclude
What it can do:
- Rank your largest excursions by size and show when they happened.
- Show your median day as an AGP, time in range, variability and overnight shape.
- Read LibreView, Dexcom Clarity, Stelo, Lingo, SiBionics, Apple Health or any CSV with times and readings.
What it cannot do:
- Know what you ate, what you were doing or how you slept.
- Prove that a spike is harmful or abnormal by itself.
- Distinguish food from stress, illness, exercise, medication, sensor lag or a bad reading.
Large observational studies find healthy adults spend about 3 hours a day above 140 mg/dL. A single rise past that line is common. Do not read a single large spike as a diagnosis.
What to check after you find your biggest spike
Open the timestamp first. If the rise started within an hour or two of food, inspect that meal. If it happened during an overnight fast or around training, treat it as a different signal.
- Same meal on different days: repeat offenders matter more than one-off spikes.
- Meal composition: fat and protein delay the peak. Refined carbohydrate tends to push it faster. Check the shape as well as the size.
- Baseline before the rise: a low baseline allows a larger rise. A high baseline with a small rise is a different problem.
- Sensor artifacts: sudden overnight drops that snap back when you roll over are compression lows, not glucose excursions.
- Context: stress, poor sleep and illness raise glucose independent of food. If there is no meal within two hours, look there next.
The obvious next step
Open your own file before you go hunting manually. If you already wear a sensor, drop the export at the free CGM report and you will see your biggest rises next to your AGP, time in range and variability. If you do not have a sensor yet, HealthOS Sensor is a month of continuous glucose with the app for $70, no membership.
Written by
HealthOS Research