# Brain fog, mood changes and poor sleep at 43: could it be perimenopause?

How perimenopause can affect concentration, mood and sleep, and why the symptom pattern matters more than one hormone result.

Canonical: https://velri.co/blog/perimenopause-brain-fog-mood-insomnia-43-provider-evaluation
Publisher: Velri (https://velri.co/about)
Published: 2026-06-19
Updated: 2026-09-30
Editorial policy: https://velri.co/editorial-policy

Perimenopause can include trouble concentrating, mood changes and disrupted sleep. At 43, it is a possible explanation worth assessing, especially when periods are changing too. Those symptoms do not identify one cause on their own. [1][2]

## The pattern gives the symptoms context

The Menopause Society describes brain fog during the transition as problems with word-finding, memory, attention or distractibility. These changes are commonly reported and are usually mild. It also notes increased vulnerability to depression during this period, particularly in people with a previous history of depression. [1]

Night sweats, changing periods and sleep disruption can be part of the same transition. Recording when each began helps show whether they follow a related pattern. [1][2]

## What an evaluation can clarify

Poor sleep, persistent fatigue and low mood also warrant attention in their own right. MedlinePlus lists sleep disorders, depression, iron deficiency, anemia and thyroid disorders among possible causes of fatigue. The assessment begins with symptoms and medical history, with tests selected for the possibilities that history raises. [3]

For example, a report of heavy bleeding creates a different question from repeated awakenings with night sweats. Both deserve a clear description.

## Why one hormone draw may not settle it

Hormone levels fluctuate during the menopause transition, which limits what one measurement can establish. [2] Testing may have a role when menopause is suspected before 45 or when the cause of symptoms is unclear; FSH is interpreted with age, history and other findings. [4]

The useful result is an explanation that connects the timing, cycle changes, sleep and mood symptoms, while identifying anything that needs separate assessment. [2][4]

## Sources
[1] Perimenopause | The Menopause Society (2026). https://menopause.org/patient-education/menopause-topics/perimenopause
[2] Menopause basics | Office on Women's Health (2023). https://www.womenshealth.gov/menopause/menopause-basics
[3] Fatigue: MedlinePlus Medical Encyclopedia (2025). https://medlineplus.gov/ency/article/003088.htm
[4] Follicle-Stimulating Hormone (FSH) Levels Test: MedlinePlus Medical Test (2023). https://medlineplus.gov/lab-tests/follicle-stimulating-hormone-fsh-levels-test/

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