As a volunteer firefighter I am occasionally called out at night. That gave me an unplanned experiment: what happens to the readings after broken sleep?
What I did
Six nights with a callout, compared with the mornings before and after. I changed nothing else — same breakfast, same routine.
What I saw
The morning readings sat around 19 mg/dl higher than on undisturbed nights. The effect showed up on the same morning and had usually settled by the following day.
What might explain it
Short sleep raises cortisol, and cortisol raises blood sugar. That is well documented. Whether the callout itself, the interrupted sleep or the physical exertion mattered most, I cannot separate — all three happened at once.
What I keep from it
I no longer read a single high morning value as a failure. Sometimes it simply says: last night was short.
The stated magnitude is a personal observation from my sensor history. The complete reproducible raw-data record for the period, comparison days and evaluation is not yet available for this release. The number is therefore not treated as confirmed research, generally transferable or a recommendation.
A single observation with my own sensor. It shows what happened to me — not what applies generally. Sleep, stress and the previous day influence every reading.
Key points
- Six nights with callouts: morning readings around 19 mg/dl higher.
- The effect appeared the same morning and usually settled within a day.
- Callout, broken sleep and exertion cannot be separated here.
- A high morning reading is not always about food.
Single observation, not a study.
The values in this article come from my own sensor (FreeStyle Libre 3) and are a single-case observation (n = 1) – they show a pattern in me, not a rule for you. Every statement is labelled as established, plausible or open, and proximity in time never counts as proof of a cause. How I handle time windows, sensor lag, influencing factors and approval is collected on one page. Read the methodology
Sources
This entry is based on my own sensor readings. Where studies are mentioned, they are linked in the text. Continuous glucose monitoring: FreeStyle Libre 3.