# Night shifts and glucose: what an energy crash can tell you

Night work can affect glucose regulation, but fatigue alone cannot identify high or low blood sugar. Research findings and diagnostic tests differ.

Canonical: https://velri.co/blog/night-shift-glucose-swings-nurse-fatigue-biomarkers
Publisher: Velri (https://velri.co/about)
Published: 2026-07-03
Updated: 2026-09-30
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Night work can change the body's response to food, including glucose regulation. But an energy crash does not identify a glucose problem by itself. Fatigue and sleepiness have several possible causes, and the symptom needs to be distinguished from a measured blood-sugar change. [1][2]

## What have controlled studies found?

A randomized crossover study in 12 healthy nurses compared mixed-meal responses during simulated day and night shifts. Glucose rose more after the meal during the night condition, and the researchers observed differences in insulin secretion. [1]

Another controlled study in chronic shift workers separated the effects of internal circadian timing from the imposed sleep-and-meal schedule. Circadian misalignment independently reduced glucose tolerance. [3]

These studies measured responses to meals under controlled conditions; they did not diagnose the cause of individual fatigue episodes. [1][3]

## Which tests answer the clinical question?

Prediabetes and diabetes are commonly assessed with HbA1c, fasting plasma glucose or an oral glucose-tolerance test. Tests of insulin resistance itself are used mainly in research, according to NIDDK. [4]

The appropriate test depends on the question, risk factors and clinical circumstances. [4]

## What is useful to record?

Describe when the symptom occurs relative to sleep, meals, caffeine and work. Note whether it is a need to sleep, a lack of physical energy or another sensation. MedlinePlus distinguishes drowsiness from fatigue, which can help make the description more precise. [2]

Include any existing glucose results and the conditions under which they were collected. A fasting result and one obtained after eating do not represent the same measurement. [4]

## Sources
[1] Glucose metabolism during rotational shift-work in healthcare workers. (2017). https://pubmed.ncbi.nlm.nih.gov/28551698/
[2] Fatigue: MedlinePlus Medical Encyclopedia (2025). https://medlineplus.gov/ency/article/003088.htm
[3] Effects of the Internal Circadian System and Circadian Misalignment on Glucose Tolerance in Chronic Shift Workers. (2016). https://pubmed.ncbi.nlm.nih.gov/26771705/
[4] Insulin Resistance & Prediabetes - NIDDK (2025). https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance

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