The Four Phases of Your Menstrual Cycle Explained

Phase 1: Menstrual Phase (Days 1-5)

The menstrual phase marks the beginning of your cycle. Day 1 is the first day of your period -- the first day you see red menstrual blood (not spotting). This phase typically lasts 3-7 days. If you are using our ovulation calculator, entering the first day of your period is the key starting point for all the cycle predictions.

What Happens During Menstruation

When pregnancy doesn't occur in the previous cycle, hormone levels (estrogen and progesterone) drop sharply. This drop signals the uterine lining (endometrium) to shed, resulting in menstrual bleeding. During this phase:

• The thickened uterine lining breaks down and is expelled
• Blood, tissue, and mucus exit through the cervix and vagina
• Estrogen and progesterone are at their lowest levels
• FSH (follicle-stimulating hormone) begins to rise toward the end of menstruation

Common Symptoms

Many women experience symptoms during menstruation. According to the NHS, the most commonly reported symptoms include:

• Menstrual cramps (dysmenorrhea) caused by uterine contractions
• Lower back pain
• Bloating and water retention
• Fatigue and low energy
• Headaches or mood changes
• Breast tenderness (usually resolving as bleeding starts)

What's Normal?

Normal menstrual bleeding typically involves 30-80 mL of blood loss over 3-7 days. Blood color may range from bright red to dark brown or even black (older blood). If you soak through a pad or tampon every hour for several hours, experience periods lasting more than 7 days, or have severe pain, consult a healthcare provider.

Complete Phase Reference Table

The table below provides a quick-reference comparison of all four cycle phases across key characteristics. This can be a helpful tool when you are learning to recognize ovulation signs or tracking changes throughout your cycle.

Phase 2: Follicular Phase (Days 1-13)

The follicular phase overlaps with the menstrual phase and continues until ovulation. It's named for the follicles -- small sacs in your ovaries that contain immature eggs. This is often considered the "spring" of your cycle, a time of renewal and building energy.

What Happens During the Follicular Phase

This phase is all about preparing for ovulation:

• FSH rises: The pituitary gland releases follicle-stimulating hormone
• Follicles develop: FSH stimulates 5-20 follicles to begin maturing in your ovaries
• One follicle dominates: Usually, one follicle becomes the "dominant" follicle and continues developing while others regress
• Estrogen increases: The growing follicle produces increasing amounts of estrogen
• Uterine lining rebuilds: Rising estrogen triggers the endometrium to thicken in preparation for a potential embryo

Follicular Phase Length Varies

While the luteal phase is relatively consistent (12-16 days), the follicular phase is variable. This is why cycle lengths differ between women and can vary from cycle to cycle in the same woman. Factors that can affect follicular phase length include:

• Age (follicular phase tends to shorten with age)
• Stress
• Illness
• Travel and time zone changes
• Significant weight changes
• Hormonal conditions like PCOS

If your cycles are irregular, the follicular phase is almost always the part of the cycle that is varying in length. Understanding this can be tremendously helpful for predicting ovulation.

How You Might Feel

As estrogen rises, many women experience:

• Increasing energy levels
• Improved mood and mental clarity
• Greater motivation and confidence
• Cervical mucus becomes wetter and more fertile as ovulation approaches

Phase 3: Ovulation Phase (Around Day 14)

Ovulation is the main event of your cycle -- when a mature egg is released from the ovary. This is your most fertile time and the only time conception can occur. For a deeper dive into this topic, see our guide on menstrual cycles and ovulation.

The Ovulation Process

Ovulation is triggered by a surge in luteinizing hormone (LH):

1. Estrogen peaks: High estrogen from the dominant follicle triggers the pituitary gland
2. LH surge: A sudden surge of LH occurs, detectable by ovulation predictor kits
3. Follicle ruptures: About 24-36 hours after the LH surge, the dominant follicle ruptures
4. Egg release: The mature egg is released into the fallopian tube
5. Egg survival: The egg survives only 12-24 hours after release

The Fertile Window

Your fertile window spans about 6 days: the 5 days before ovulation plus ovulation day. This is because sperm can survive in the reproductive tract for up to 5 days. The most fertile days are:

• 2 days before ovulation: ~25% conception chance
• 1 day before ovulation: ~33% conception chance (peak)
• Ovulation day: ~30% conception chance

Signs of Ovulation

Your body provides signals that ovulation is approaching or occurring. Recognizing these signs of ovulation is one of the most valuable skills you can develop for fertility awareness:

• Cervical mucus becomes clear, stretchy, and egg-white-like
• Cervix rises, softens, and opens
• Some women feel ovulation pain (mittelschmerz) on one side
• Slight increase in basal body temperature after ovulation
• Increased libido
• Positive ovulation predictor kit (detects LH surge)

Calculating Ovulation Day

Ovulation typically occurs 14 days before your next period (not 14 days after your last period). For a 28-day cycle, that's day 14. For a 30-day cycle, it's day 16. For a 26-day cycle, it's day 12. Use our ovulation calculator to estimate your ovulation date and see your full fertile window mapped out.

Phase 4: Luteal Phase (Days 15-28)

The luteal phase begins after ovulation and lasts until your next period. It's typically 12-16 days long (average 14 days) and is relatively consistent from cycle to cycle for each individual. To learn more about how long this phase lasts and what to expect, read our article on how long after ovulation your period comes.

What Happens During the Luteal Phase

After the egg is released, the empty follicle transforms:

• Corpus luteum forms: The ruptured follicle becomes a temporary gland called the corpus luteum
• Progesterone rises: The corpus luteum produces progesterone (and some estrogen)
• Uterine lining matures: Progesterone causes the endometrium to thicken further and become receptive to a fertilized egg
• Body temperature rises: Progesterone causes a slight increase in basal body temperature (0.5-1 degrees F)

If Conception Occurs

If the egg is fertilized and implants in the uterine lining:

• The embryo begins producing hCG (human chorionic gonadotropin)
• hCG signals the corpus luteum to keep producing progesterone
• Progesterone maintains the uterine lining to support the pregnancy
• Eventually, the placenta takes over hormone production

If Conception Doesn't Occur

If the egg isn't fertilized (or doesn't implant):

• The corpus luteum degrades after about 10-14 days
• Progesterone and estrogen levels drop sharply
• The drop in hormones triggers the uterine lining to shed
• Menstruation begins, starting a new cycle

Luteal Phase Symptoms (PMS)

Many women experience premenstrual symptoms during the luteal phase:

• Breast tenderness and swelling
• Bloating and water retention
• Mood changes, irritability, or anxiety
• Food cravings
• Fatigue
• Headaches
• Acne flare-ups

These symptoms are caused by the hormonal fluctuations, particularly the rise and fall of progesterone.

Luteal Phase Defect

A luteal phase shorter than 10 days may indicate a "luteal phase defect," where the corpus luteum doesn't produce enough progesterone to support a potential pregnancy. If you're trying to conceive and tracking shows a consistently short luteal phase, consult a healthcare provider.

Key Hormones Explained

Four main hormones orchestrate your menstrual cycle. Understanding how they interact is essential for interpreting your body's signals -- from changes in cervical mucus to shifts in your basal body temperature.

The Feedback Loop

These hormones work together in a feedback loop:

1. Low estrogen and progesterone signal the brain to produce FSH
2. FSH stimulates follicle growth, which produces estrogen
3. Rising estrogen eventually triggers the LH surge
4. LH surge causes ovulation
5. The corpus luteum produces progesterone
6. If no pregnancy, progesterone drops, and the cycle restarts

Tracking Your Cycle

Understanding your personal cycle patterns can help with fertility awareness, symptom management, and overall health awareness.

What to Track

• Period dates: First and last day of bleeding
• Flow amount: Light, medium, or heavy
• Cervical mucus: Type and amount daily
• Basal body temperature: Before getting out of bed
• Symptoms: Cramps, mood, energy, etc.
• Ovulation test results: If using OPKs

Benefits of Cycle Tracking

• Identify your fertile window for conception or avoidance
• Predict your next period
• Spot irregularities that may need medical attention
• Understand your personal symptom patterns
• Optimize activities and self-care around your cycle

Our ovulation calculator can help you estimate your fertile window and predict key cycle dates based on your cycle length. For the most accurate picture, combine the calculator with your own observations of cervical mucus and basal body temperature.

Cycle Syncing: Optimizing Your Life Around Your Phases

Cycle syncing is the practice of adjusting your exercise, nutrition, productivity, and social activities to match the hormonal shifts that occur during each phase of your menstrual cycle. Rather than fighting against natural energy fluctuations, cycle syncing works with them -- and many women find it transformative for both physical performance and emotional well-being.

The concept is grounded in well-established science: estrogen and progesterone have measurable effects on metabolism, mood, muscle recovery, and cognitive function. While large-scale clinical trials specifically on "cycle syncing" as a unified protocol are still emerging, the underlying hormonal influences are thoroughly documented by organizations like the World Health Organization and the Mayo Clinic.

Exercise by Phase

Your body responds differently to exercise depending on where you are in your cycle. During the follicular phase and around ovulation, rising estrogen supports muscle building, endurance, and faster recovery. During the luteal phase, elevated progesterone raises your core temperature, increases perceived exertion, and makes recovery slower. Adjusting your workout intensity accordingly can help you train smarter, not just harder.

Nutrition by Phase

Hormonal shifts also change your nutritional needs. For example, iron-rich foods are especially important during and after menstruation to replenish what is lost through bleeding. In the luteal phase, your body's caloric needs increase slightly (by roughly 100-300 calories per day), and cravings for complex carbohydrates are a natural response to support serotonin production as progesterone rises.

Productivity and Social Energy by Phase

Many women report that their cognitive strengths shift throughout the cycle. The late follicular phase and ovulation tend to bring verbal fluency, creativity, and social confidence -- making them ideal for presentations, brainstorming, and networking. The luteal phase, particularly the late luteal phase, often favors detail-oriented work, editing, and completing tasks that require focus rather than novelty.

Exercise and Nutrition Guide by Phase

Mood, Energy, and Cognitive Strengths by Phase

Remember, cycle syncing is about awareness, not rigid rules. Every woman's experience is unique, and the best approach is to observe your own patterns over several cycles and adjust gradually. Tracking your symptoms alongside your cycle using our calculator is a great way to start building this self-knowledge.

How Cycle Length Affects Phase Duration

One of the most important things to understand about the menstrual cycle is that not all phases change equally when cycle length varies. The luteal phase is remarkably consistent -- almost always lasting 12 to 16 days regardless of total cycle length. This means that when your cycle is shorter or longer than 28 days, it is the follicular phase that expands or contracts.

For a woman with a 21-day cycle, the follicular phase may last only about 7 days, meaning ovulation occurs early -- around day 7. For a woman with a 35-day cycle, the follicular phase stretches to about 21 days, and ovulation doesn't occur until around day 21. This is why the common advice that "ovulation happens on day 14" can be misleading -- it is only accurate for a textbook 28-day cycle.

As you can see from the chart above, shorter cycles compress the follicular phase, which means the fertile window arrives much sooner after menstruation. In very short cycles, the fertile window can even overlap with the end of your period. Longer cycles delay the fertile window, which is important information if you are trying to determine when you ovulate after your period.

This is exactly why using our ovulation calculator with your actual cycle length (rather than assuming 28 days) gives you much more accurate fertile window predictions. And if your cycles are irregular, combining the calculator with cervical mucus and BBT tracking provides the most complete picture.

When Phase Patterns Signal Health Issues

While some cycle variation is perfectly normal, certain patterns in your menstrual phases can indicate underlying health concerns. The Healthline medical team and the Planned Parenthood both emphasize that paying attention to cycle patterns is one of the most accessible forms of health monitoring. Here are the warning signs to watch for.

Absent Menstrual Phase (Amenorrhea)

If you miss three or more consecutive periods (and you are not pregnant, breastfeeding, or menopausal), this is called secondary amenorrhea. Possible causes include excessive exercise, very low body weight, high stress, thyroid disorders, polycystic ovary syndrome (PCOS), or premature ovarian insufficiency. Amenorrhea can also affect bone density over time, so it is important to seek evaluation.

Very Short or Very Long Follicular Phase

A follicular phase consistently shorter than 10 days (leading to very short cycles of 21 days or less) may indicate diminished ovarian reserve, commonly seen with advancing age. A very long follicular phase (resulting in cycles over 35 days) can signal hormonal imbalances such as PCOS, thyroid dysfunction, or hypothalamic amenorrhea. Both extremes deserve medical attention, particularly if you are trying to conceive.

Short Luteal Phase Defect

As discussed in the luteal phase section, a luteal phase shorter than 10 days may not allow sufficient time for embryo implantation. If BBT tracking consistently shows a short post-ovulation temperature rise, this is worth discussing with a healthcare provider. Treatment options may include progesterone supplementation or ovulation induction medications.

Anovulatory Cycles

Some women experience cycles where ovulation does not occur at all. You may still bleed (called anovulatory bleeding), but the bleeding is not a true period following the normal hormonal sequence. Signs of an anovulatory cycle include absent or very irregular cervical mucus changes, no BBT shift, and cycles that vary dramatically in length. Occasional anovulatory cycles can be normal (especially during stress, illness, or the perimenopausal transition), but frequent anovulation warrants investigation.

When to See a Doctor

You should consult a healthcare provider if you experience:

• Cycles consistently shorter than 21 days or longer than 35 days
• Periods that last longer than 7 days
• Extremely heavy bleeding (soaking through a pad or tampon every hour)
• Severe pelvic pain that interferes with daily activities
• Spotting between periods or after intercourse
• Absence of periods for 3 or more months
• Signs of anovulation when trying to conceive

For a more comprehensive guide on when professional help is needed, read our article on when to see a fertility specialist.

Hormone Reference Ranges by Phase

Knowing the approximate hormone levels expected during each phase of your cycle can be helpful when interpreting lab results or understanding why you feel the way you do at different times of the month. The table below provides detailed reference ranges for the four primary reproductive hormones across all four cycle phases. These values are based on standard clinical reference ranges as reported by the NIH's National Institute of Child Health and Human Development (NICHD) and major clinical laboratories.

What These Ranges Mean for You

Understanding hormone reference ranges can help you have more productive conversations with your healthcare provider. For example:

• High FSH on day 2-3: May indicate diminished ovarian reserve, especially if above 10-15 mIU/mL
• LH surge detection: Ovulation predictor kits detect when LH rises above your personal baseline, typically to 25-40 mIU/mL or higher
• Mid-luteal progesterone above 3 ng/mL: Confirms that ovulation occurred; levels above 10 ng/mL suggest strong ovulation
• Low estradiol: May be seen in hypothalamic amenorrhea, premature ovarian insufficiency, or during perimenopause

For more on how these hormonal shifts affect your daily experience, see our comprehensive guide to the menstrual cycle and ovulation.

Phase-Specific Symptoms

Every phase of your menstrual cycle comes with its own set of physical and emotional symptoms driven by hormonal changes. While the symptoms listed in the complete phase reference table earlier in this article provide a quick summary, the table below goes into greater detail, including less common symptoms and guidance on when a symptom may warrant medical attention.

Exercise and Nutrition by Cycle Phase

Your body's hormonal environment changes significantly throughout your menstrual cycle, and these shifts affect everything from your exercise tolerance and recovery speed to your nutritional needs and food cravings. The table below provides a comprehensive, phase-by-phase guide to help you optimize your fitness and nutrition. This expands on the cycle syncing concepts discussed earlier in this article with more specific, actionable recommendations.

For additional context on how the hormones driving these changes interact throughout your cycle, see our detailed article on the menstrual cycle and ovulation explained. And for guidance on tracking your basal body temperature, which can confirm when you have transitioned from the follicular phase into the luteal phase, see our BBT tracking guide.

Hormone Levels Throughout Each Phase

Understanding how hormone concentrations rise and fall across the four cycle phases provides valuable context for interpreting your body's signals. According to the World Health Organization (WHO), the interplay between estrogen, progesterone, FSH, and LH orchestrates every aspect of the menstrual cycle -- from follicle development to uterine lining preparation to ovulation itself. The chart below illustrates the relative levels of each hormone across the four phases, helping you visualize the hormonal landscape that drives ovulation signs and fertile window timing.

The following table provides specific reference ranges for each major reproductive hormone across the four cycle phases. These ranges are approximate and can vary between laboratories. As the Royal College of Obstetricians and Gynaecologists (RCOG) notes, always interpret blood test results with your healthcare provider in the context of the specific cycle day the sample was drawn.

These hormone dynamics explain why you experience the physical changes documented in our signs of ovulation guide. Rising estrogen in the follicular phase drives fertile cervical mucus production, while the LH surge detected by OPKs signals imminent ovulation. The post-ovulation rise in progesterone is what causes the BBT shift that confirms ovulation occurred.

How Each Phase Affects Body and Mood

Your menstrual cycle does not just affect your reproductive system -- it influences nearly every aspect of your physical and emotional well-being. According to Healthline, the hormonal fluctuations across cycle phases create predictable patterns in energy, mood, cognitive function, and even skin quality. Understanding these patterns can help you plan your activities, manage expectations, and practice cycle-aware self-care. The WebMD guide on menstrual hormones provides additional clinical context for these effects.

These patterns are generalizations based on hormonal research, and every woman's experience will differ. The practice of cycle syncing -- adjusting your activities to match these natural patterns -- has gained significant popularity. While rigorous clinical trials are still limited, many women report that working with their cycle rather than against it leads to improved performance, better mood management, and reduced PMS severity. For more about recognizing the physical signals your body provides around ovulation, see our guides on ovulation signs and how long after ovulation your period comes.

Abnormal Phase Patterns

While natural variation in cycle length and symptoms is completely normal, certain patterns may signal underlying health conditions that warrant medical attention. According to NICE (National Institute for Health and Care Excellence) clinical guidelines, specific menstrual irregularities should prompt evaluation by a healthcare provider. The table below outlines the most clinically significant abnormal patterns, their potential causes, and recommended actions.

If you notice any of these patterns, do not delay seeking evaluation. As the RCOG emphasizes, the menstrual cycle is a vital sign -- and persistent abnormalities often indicate treatable conditions. Tracking your cycle with a fertility app provides your healthcare provider with objective data that speeds diagnosis. For women trying to conceive, our guide on when to see a fertility specialist outlines specific thresholds for seeking help, and our ovulation with irregular periods article provides strategies for managing fertility tracking with non-standard cycles.

Related Reading

Explore all of our in-depth guides on the menstrual cycle, ovulation, and reproductive health:

• Ovulation Calculator -- Free tool to predict your fertile window and ovulation date
• About Ovulation Calculator -- Learn about our mission and methodology
• The Menstrual Cycle and Ovulation Explained
• Fertile Window: When Are You Most Likely to Conceive?
• Signs of Ovulation: How to Know When You're Fertile
• Due Date Calculator Based on Ovulation Date
• How Many Days After Your Period Do You Ovulate?
• Basal Body Temperature and Ovulation
• Cervical Mucus and Fertility
• OPK Ovulation Predictor Kits
• Irregular Periods and Ovulation
• Ovulation With Irregular Periods
• How Long After Ovulation Is Your Period?
• Due Date Calculation Methods Compared
• Clearblue Ovulation Calculator Guide
• Best Fertility Tracker Apps
• When to See a Fertility Specialist

Frequently Asked Questions