The Kindr Cycle · Stage
Periods
The monthly cycle is a vital sign — not just a nuisance.
What's happening in your body
A menstrual cycle is the roughly monthly rise and fall of estrogen and progesterone that prepares the uterus for a possible pregnancy. It starts on the first day of bleeding and ends the day before the next period begins. Per ACOG, a typical cycle lasts 21 to 35 days in adults, with 2 to 7 days of bleeding.
The cycle has two halves. In the follicular phase, follicle-stimulating hormone (FSH) recruits ovarian follicles and estrogen rises to build the uterine lining. Around mid-cycle, a surge of luteinizing hormone (LH) triggers ovulation — the release of a mature egg. In the luteal phase, the empty follicle becomes the corpus luteum and produces progesterone, stabilizing the lining. If pregnancy does not occur, the corpus luteum breaks down, hormones drop, and the lining sheds as a period (NIH).
The American College of Obstetricians and Gynecologists formally endorses treating the menstrual cycle as a vital sign — as informative about overall health as heart rate or blood pressure.
What's common
Cycle length varies. A cycle can be 24 days one month and 32 the next in the same person and still be normal. What matters is a pattern that fits within the 21–35-day range for adults (ACOG).
Cramping (dysmenorrhea) affects up to 90% of menstruating people at some point (CDC). Mild to moderate cramps that respond to over-the-counter NSAIDs and do not interfere with life are within normal range.
PMS symptoms — mood changes, bloating, breast tenderness, food cravings — affect an estimated 3 in 4 people during reproductive years (Office on Women's Health, HHS). PMDD is a more severe form affecting about 3–8%.
Cycles are often irregular in the first few years after menarche and in the years leading up to menopause — this is expected, not automatically a problem.
What deserves a conversation
Talk with a licensed provider about:
- Cycles shorter than 21 days, longer than 35 days, or missing for 3+ months without an obvious cause (like breastfeeding, contraception, or pregnancy).
- Bleeding that soaks through a pad or tampon every hour for several hours, passes clots larger than a quarter, or lasts more than 7 days (ACOG's definition of heavy menstrual bleeding).
- Pain that stops you from working, sleeping, or functioning — especially if NSAIDs don't help. This can be a sign of endometriosis, fibroids, or adenomyosis, all of which are treatable.
- Bleeding between periods, after sex, or after menopause. These warrant a workup.
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Common questions
Is a 35-day cycle normal?
Yes, per ACOG, adult cycles between 21 and 35 days are within normal range. Track for a few months — consistency matters more than a specific number.
How much bleeding is too much?
Heavy menstrual bleeding (menorrhagia), per ACOG, is bleeding that soaks through a pad or tampon every hour for several consecutive hours, lasts more than 7 days, or requires double protection. Any of these deserve a workup.
When do cycles become irregular before menopause?
Cycle changes are typically the first sign of perimenopause and can start in the mid-40s (some earlier). Cycles may shorten, lengthen, or become unpredictable for years before periods stop entirely (NIH National Institute on Aging).
Sources
Medically reviewed by Dr. Ana Lisa Carr, MD, MBA · Last reviewed July 14, 2026