Learn everything you need to know about your menstrual cycle. Understanding it is essential as it impacts every aspect of your well-being.
Reviewed by Jasveer Matharu · 1 November 2026
Updated cycle phase explanations, added comparison tables and the shared phase graphic, and linked the reviewed evidence.
First published
In this post, we will cover everything you need to know about your menstrual cycle.
Key points covered:
Important:
By definition, the menstrual cycle begins with the first day of your period, which is counted as ‘Day 1’ and ends just before the next period (bleeding).
It’s the female body’s way of preparing for a possible pregnancy every month.
Understanding your cycle is very important as it impacts every aspect of female well-being, including hunger and sleep.
As the hormones in your cycle change throughout the month, your body and mind also go through a number of changes.
Menstrual cycles often last around 28 days, but regular cycles from 21 to 35 days are normal. Timing can vary between people and from one cycle to the next.
A 28-day cycle is an example, not a rule. The NHS describes periods as irregular when the gap between their starts is less than 21 days or more than 35 days. Cycles are often more irregular in the years after periods begin and as menopause approaches. Speak to your GP or doctor if your usual pattern changes or your periods are irregular.
The ovarian cycle has two main phases: the follicular phase, from the first day of your period to ovulation, and the luteal phase, after ovulation until the next period. Ovulation marks the transition between them. For consistency with our cycle syncing guide, we explain four selected hormonal windows below: early follicular (menstrual), late follicular, mid-luteal and late luteal (premenstrual), with a separate explanation of ovulation. Researchers subdivide the cycle in different ways; this is not a universal four- or five-phase classification.
See the research behind this recommendationRead the evidence on phase names, timing and symptoms.
For more detailed information on the Luteal Phase, check out our complete article: Luteal Phase - What It Is and How It Impacts You
The menstrual cycle is regulated by several different hormones. But the main ones are:
| Hormone | Main role in the cycle | Typical pattern |
|---|---|---|
| FSH (follicle-stimulating hormone) | Helps ovarian follicles grow; each contains an immature egg. | Rises as a new cycle approaches, then helps recruit follicles early in the follicular phase. |
| Estrogen (mainly estradiol) | Helps rebuild the uterine lining after menstruation. | Rises before ovulation, then has a smaller second rise during the luteal phase. |
| LH (luteinizing hormone) | An LH surge helps trigger egg release. | Surges before ovulation; afterward it supports the corpus luteum. |
| Progesterone | Helps prepare and maintain the uterine lining for a possible pregnancy. | Rises after ovulation, usually peaks mid-luteal, then falls if pregnancy does not occur. |
This is a simplified pattern for a cycle with ovulation. Hormone levels and timing vary; the table cannot identify your phase or diagnose a hormone problem.
See the research behind this recommendationRead the evidence behind the hormone summary.
Follicle-stimulating hormone is produced by the pituitary gland. It regulates the functions of both the ovaries and the testes. Lack or insufficiency of it can cause infertility in both men and women.
Follicle-stimulating hormone is one of the gonadotropic hormones, the other being the luteinizing hormone, and both are released by the pituitary gland into the bloodstream.
Follicle-stimulating hormone is essential to pubertal development. In women, this hormone stimulates the growth of ovarian follicles in the ovary before the release of an egg and it also increases a type of estrogen.
Estrogen is one of the main female sex hormones. While both women and men produce estrogen, it plays a bigger role in women’s bodies.
It has many roles in the body, from controlling puberty to strengthening bones. Having too much or too little estrogen can cause a range of different medical conditions (opens in a new tab).
There are three estrogens – estrone, estradiol, and estriol – the most potent of which is estradiol.
Estradiol is a steroid hormone made from cholesterol and is the strongest of the three naturally produced estrogens. It is the main estrogen found in women and has many functions, although it mainly acts to mature and maintain the female reproductive system. A natural increase in blood estradiol concentrations during the menstrual cycle causes an egg to mature and be released.
Another important role of estradiol is to thicken the lining of the uterus so that the egg can implant if it becomes fertilized. Estradiol also promotes the development of breast tissue and increases both bone and cartilage density.
In premenopausal women, estradiol is mostly made by the ovaries. Estradiol levels vary throughout the menstrual cycle, rising to a peak before ovulation and showing a smaller second rise in the luteal phase. Levels are relatively low during menstruation. Estradiol levels change during the transition to menopause and are generally lower afterward. In pregnant women, the placenta also produces estradiol, especially toward the end of pregnancy.
Men also produce estradiol; however, the amounts produced are much lower than in women. Within the testes, some testosterone is changed into estradiol and this estradiol is essential for the production of sperm. In both sexes, estradiol is also made in much smaller amounts by fat tissue, the brain, and the walls of blood vessels.
Luteinizing hormone, like a follicle-stimulating hormone, is a gonadotrophic hormone produced and released by cells in the anterior pituitary gland.
It is crucial in regulating the function of the testes in men and ovaries in women.
In women, luteinizing hormone carries out different roles during the follicular and luteal phases. During the follicular phase, it helps the ovarian follicles produce hormones involved in the cycle, including estradiol.
An LH surge helps trigger the release of a mature egg from the ovary, a process called ovulation. This marks the transition from the follicular to the luteal phase; it does not always happen on day 14.
After ovulation, the remnants of the ovarian follicle form a corpus luteum.
The luteinizing hormone stimulates the corpus luteum to produce progesterone, which is required to support the early stages of pregnancy if fertilization occurs.
Progesterone belongs to a group of steroid hormones called progestogens. It is mainly secreted by the corpus luteum in the ovary during the luteal phase of the menstrual cycle.
It plays an important role in the menstrual cycle and in maintaining the early stages of pregnancy.
During the menstrual cycle, when an egg is released from the ovary at ovulation, the remnants of the ovarian follicle that enclosed the developing egg form a structure called the corpus luteum. This releases progesterone and estrogen. Progesterone usually peaks around a week after ovulation, in the mid-luteal phase.
Progesterone prepares the body for pregnancy in the event that the released egg is fertilized.
If pregnancy does not occur, the corpus luteum breaks down during the late luteal phase, progesterone and estrogen fall, and the next period begins.
If the egg is fertilized, progesterone stimulates the growth of blood vessels that supply the lining of the womb (endometrium) and stimulates glands in the endometrium to secrete nutrients that nourish the early embryo.
Progesterone then prepares the tissue lining of the uterus to allow the fertilized egg to implant and helps to maintain the endometrium throughout pregnancy.
During the early stages of pregnancy, progesterone is still produced by the corpus luteum and is essential for supporting the pregnancy and establishing the placenta. Once the placenta is established, it then takes over progesterone production at around weeks 8-12 of pregnancy.
During pregnancy, progesterone plays an important role in the development of the fetus; it stimulates the growth of maternal breast tissue; prevents lactation; and strengthens the pelvic wall muscles in preparation for labor.
The level of progesterone in the body steadily rises throughout pregnancy until labor occurs and the baby is born.
Although the corpus luteum in the ovaries is the major site of progesterone production in humans, progesterone is also produced in smaller quantities by the ovaries themselves, the adrenal glands, and, during pregnancy, the placenta.
Your menstrual cycle is your personal algorithm of life. Take time to learn about how changing hormones impact you throughout the cycle (we call this menstrual cycle literacy) to understand how you can take advantage of your hormones instead of suffering through them.
You might also be interested in the following article:
Phase definitions and timing: Elliott-Sale et al. 2021: Table 3 (opens in a new tab) · McNulty et al. 2020: phase definitions (opens in a new tab) · Elliott-Sale et al. 2026: Table 1 (opens in a new tab) · NHS: cycle length, bleeding and ovulation (opens in a new tab) · NHS: irregular periods and when to seek care (opens in a new tab) · NHS: PMS symptoms and care (opens in a new tab) · NHS: period pain and practical self-care (opens in a new tab)
Hormone summary: Hormone roles: Society for Endocrinology — menstrual-cycle overview (opens in a new tab) · FSH: growth of ovarian follicles (opens in a new tab) · Estradiol: rebuilding the uterine lining (opens in a new tab) · LH: the surge before ovulation (opens in a new tab) · Progesterone: corpus luteum and uterine lining (opens in a new tab)
Explore the findings and sources for each recommendation.
These notes explain the research and guidance behind the article, what they support and where uncertainty remains.
Two assessments cover the phase terminology, timing and hormone summary updated here. They do not constitute a new comprehensive appraisal of every hormone claim in this article.
Confidence describes how certain we are about a research finding. It does not measure how healthy a food is, or promise that it will work for you.
Search check: Targeted editorial checks of the supplied citations on October 29 and November 1, 2026, followed by reconciliation with the accepted article. This was not a systematic review or a formal GRADE assessment. Access limitations from that review are retained. Searched through .
What the confidence labels meanQuestion. Cycle phases, timing and terminology and Understanding the physiological sequence without fixed day ranges or individual symptom predictions in Readers learning about natural ovulatory cycles.
Finding. This update uses the same phase definitions as the Cycle Syncing article. The broad ovarian phases are follicular and luteal; menstruation overlaps early follicular, and ovulation marks the transition. Early follicular, late follicular, mid-luteal and late luteal are selected windows, with early luteal explained as the lead-in to mid-luteal. Researchers use different subdivisions, so the five explanation sections are not a universal scientific classification. The 2021 working guide describes several classification schemes and proposes four research hormone profiles; McNulty’s 2020 review uses six categories. The 2026 follow-up retains numbered profiles and distinguishes hormonal sampling from symptom-based windows. These methodological sources explain terminology; they do not establish a fixed food, workout or work-performance schedule. Timing and symptoms: NHS guidance describes regular cycles of 21–35 days, bleeding usually lasting 2–7 days, and ovulation often 10–16 days before the next period. These ranges do not confirm an individual’s ovulation day. Symptoms vary, and PMS can start before the late luteal window. Practical exercise and food examples are flexible choices; the team’s personal experiences are not predictions for every reader.
Evidence label. Evidence is indirect
Applicability. Evidence is indirect — These sources explain typical physiology and research terminology. They do not identify an individual’s hormonal phase or predict their symptoms, fertility or response to exercise.
Why no grade. This is a physiological explanation supported by endocrinology guidance and research-method papers, not a graded treatment-effect claim.
Rationale. The explanation uses the same broad follicular/luteal division and selected hormonal windows as the Cycle Syncing article. Ovulation marks the transition; early luteal leads into mid-luteal.
Limitations. Cycle timing and symptoms vary. These sources do not validate a fixed calendar or phase-specific food, workout or work-performance schedule. The update was a targeted terminology and physiology check, not a new comprehensive appraisal of every hormone claim in the article.
Safety context. The table and graphic cannot identify an individual’s phase, diagnose a hormone problem or predict fertility. Symptoms that affect daily life, irregular bleeding or a changed pattern warrant clinical advice.
Method. Elara Evidence method, version 0.1.
Search. Targeted editorial checks of the supplied citations on October 29 and November 1, 2026, followed by reconciliation with the accepted article. This was not a systematic review or a formal GRADE assessment. Access limitations from that review are retained. Searched through .
Question. Hormone roles in an ovulatory cycle and Understanding the physiological sequence without fixed day ranges or individual symptom predictions in Readers learning about natural ovulatory cycles.
Finding. Hormone summary and shared schematic: Society for Endocrinology guidance explains follicle growth, the LH surge, the corpus luteum and the uterine lining. These sources support the physiological sequence, not a fixed calendar or predictions about symptoms, performance or fertility. The table condenses the hormone roles explained above; it is not a diagnostic guide.
Evidence label. Evidence is indirect
Applicability. Evidence is indirect — These sources explain typical physiology and research terminology. They do not identify an individual’s hormonal phase or predict their symptoms, fertility or response to exercise.
Why no grade. This is a physiological explanation supported by endocrinology guidance and research-method papers, not a graded treatment-effect claim.
Rationale. The explanation uses the same broad follicular/luteal division and selected hormonal windows as the Cycle Syncing article. Ovulation marks the transition; early luteal leads into mid-luteal.
Limitations. Cycle timing and symptoms vary. These sources do not validate a fixed calendar or phase-specific food, workout or work-performance schedule. The update was a targeted terminology and physiology check, not a new comprehensive appraisal of every hormone claim in the article.
Safety context. The table and graphic cannot identify an individual’s phase, diagnose a hormone problem or predict fertility. Symptoms that affect daily life, irregular bleeding or a changed pattern warrant clinical advice.
Method. Elara Evidence method, version 0.1.
Search. Targeted editorial checks of the supplied citations on October 29 and November 1, 2026, followed by reconciliation with the accepted article. This was not a systematic review or a formal GRADE assessment. Access limitations from that review are retained. Searched through .
Confidence describes how certain we are about a research finding. It does not measure how healthy a food is, or promise that it will work for you.
Founder of Elara Care and O.A. Dip. Certified Women's Health Practitioner, Jas is working to create better solutions for women since 2018, sharing her struggles and experiences with female health
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