Why is my cycle getting shorter?
Last updated September 3, 2026.
The commonest cause is the ovarian clock: declining reserve compresses the follicle phase, so cycles shrink from 28 days toward 24 - the classic early perimenopause signal, expected physiology in the 40s. At younger ages: thyroid overactivity and stress patterns also shorten cycles, and any persistent change deserves a mention. The texture tells: perimenopausal shortening travels with sleep changes, new PMS intensity, and skipped months; thyroid changes bring racing heart, weight loss, heat intolerance. Track three months of dates - the pattern is the information - and bring it in if cycles stay under 24 days or symptoms ride along.
What to do
- Track three months of dates. The log is the diagnostic evidence.
- Frame by age. 40s: expected perimenopause physiology. Younger: check.
- Note the companion symptoms. Sleep, PMS, skipped months versus heart-racing and heat intolerance.
- Bring it in under 24 days. Thyroid and hormone blood tests are the workup.
Related questions
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