# Fatigue after weeks of overtime: what else could contribute?

Long hours can disrupt sleep, but persistent fatigue also deserves a symptom and medication review. Testing should follow the question being investigated.

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Publisher: Velri (https://velri.co/about)
Published: 2026-07-26
Updated: 2026-09-30
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Long work hours can reduce sleep opportunity and disrupt sleep quality. Persistent fatigue can also have other contributors, including anemia, thyroid problems, medicines, depression or a sleep disorder. [1][2]

The useful question is whether the pattern is fully explained by the schedule or whether something else needs investigation.

## Describe the change in function

Being sleepy during quiet moments differs from feeling physically depleted despite rest. MedlinePlus distinguishes drowsiness, the need to sleep, from fatigue, a lack of energy. [2]

Explain what is different from your usual baseline: whether ordinary tasks feel harder, whether rest helps, and when the change began. Include the actual hours available for sleep rather than only the number of hours worked.

## Which tests might be relevant?

A fatigue evaluation may use a complete blood count to investigate anemia and selected tests for thyroid, kidney or liver questions. The history and examination determine which are useful. [2]

Testing is most useful when it addresses a specific concern raised by the symptoms or history. [2]

## When cortisol testing is relevant

Cortisol testing investigates particular disorders involving too much or too little cortisol. Levels vary during the day and can be affected by stress, exercise and medicines. One value cannot identify the cause of exhaustion. [3]

The Endocrine Society also cautions that “adrenal fatigue” is not an established medical diagnosis and that tests promoted for it are unsupported. [4]

## Keep the work conditions in the assessment

Sleep duration, awakenings and timing all matter. NIOSH treats sleep that is poorly timed or repeatedly disrupted as inadequate even when the total hours appear reasonable. [1]

A useful review can therefore examine both the schedule and possible medical contributors.

## Sources
[1] Module 2. Sleep is a Basic Need | NIOSH | CDC (2020). https://www.cdc.gov/niosh/work-hour-training-for-nurses/longhours/mod2/03.html
[2] Fatigue: MedlinePlus Medical Encyclopedia (2025). https://medlineplus.gov/ency/article/003088.htm
[3] Cortisol Test: MedlinePlus Medical Test (2024). https://medlineplus.gov/lab-tests/cortisol-test/
[4] Adrenal Fatigue | Endocrine Society (2022). https://www.endocrine.org/patient-engagement/endocrine-library/adrenal-fatigue

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