Overview - a read this first section

Info

According to the International Federation of Gynecology and Obstetrics, (FIGO), a normal menstrual cycle is defined as:

- consistent frequency, regularity, duration, and volume of flow

- cycles occurring every 24-38 days

- bleeding lasting 8 days or less

Note: there is no official standard for what is considered, "heavy," or "light" flow.

Is Your Cycle Considered Regular?

Medical definition of a regular cycle is based on an average of +/- 4 days of consistency month-to-month.

Gather data from several months to see where you are in the range of every 24-38 days.

Overall, your cycle is considered regular is your difference month-to-month is between 1-4 days.

Specifics for normal fluctuation month-to-month by age ranges: ages 18-25 = up to 9; ages 19-41 = up to 7; ages 42-45 up to 9. (Yes, it's the same variability for ages 18-25 as it is for ages 42-45.) This article does not specify for ages below 18 or ages above 45.

Science Behind Reasons for Regular / Normal

The edometrium must be healthy, regular

he hypothalamus-pituitary-ovarian (HPO) axis must function properly, the endometrium must be healthy, and the uterine outflow tract must be patent. Numerous conditions can impact the HPO axis, including endocrine, metabolic, inflammatory, infectious, autoimmune, infiltrative, genetic, and neoplastic processes.

The official names of each stage in the cycle of menstruation:

Follicular

Ovulation

Luteal

Menstrual

- Day 1 is defined as the first day of heavy menstrual flow

Ovarian Cycle: follicular phase, ovulation, and luteal phase

Endometrium Cycle: proliferation phase, secretory phase, and menstrual phase

The three parts of the endometrium cycle are usually only referred to as the menstrual phase.

Source

Thiyagarajan DK, Basit H, Jeanmonod R. Physiology, Menstrual Cycle. [Updated 2024 Sep 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Website link: https://www.ncbi.nlm.nih.gov/books/NBK500020/ Accessed on 16 May 2025.

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