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    What Happens to Hormone Levels During the Menstrual Cycle?

    Updated 15 November 2023 |
    Published 26 November 2018
    Fact Checked
    Reviewed by Andrei Marhol, PhD, Flo lead medical advisor, Lithuania
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    For each cycle, the body works around the clock to prepare for a potential pregnancy. This means the brain and ovaries are constantly interacting to create hormone level changes over the course of each menstrual cycle. In this article, we’ll see which hormones dominate in different cycle phases and how they influence mental and physical fitness.

    Menstrual cycle

    The menstrual cycle is a series of regular, natural changes in the body. The length of a menstrual cycle is determined by the number of days from the first day of one period to the first day of the next. In other words, the first day of the menstrual cycle is the first day of your period.

    The menstrual cycle has two main phases. The follicular phase, or proliferative phase, normally makes up the first 10–16 days of the cycle. The luteal, or secretory, phase comes right after ovulation and lasts for about 14 days, ending with menstruation if pregnancy didn’t occur. Generally, menstrual cycles that last from 21–35 days, with a typical duration of 28 days, are considered normal.

    Important monthly cycle hormones

    The reproductive system is influenced by hormones that are regulated by the hypothalamus and the gonadotropin-releasing hormone (GnRH). GnRH causes the cells in the frontal part of the pituitary gland to produce two types of hormones.

    The first hormone is follicle-stimulating hormone (FSH), and the other is luteinizing hormone (LH). These hormones travel all the way to the ovaries, where they influence estrogen and progesterone levels and help the follicles inside the ovaries mature.

    Some of the matured follicles will eventually release eggs, which travel down the uterine tubes, where they can be fertilized before moving to the uterus. The complex hormone interaction that makes this possible is called the hypothalamic-pituitary-ovarian axis.

    At the end of a cycle right before menstruation, estrogen and progesterone levels drop, causing an increase of FSH and GnRH levels.

    All the hormones involved in the hypothalamic-pituitary-ovarian axis rise in one phase of the menstrual cycle and drop in the other. All of these fluctuations affect ovulation and can cause symptoms like acne, negative mood, headache, weight gain, bloating, and appetite changes.

    Now let’s take a look at how hormone levels change during the cycle stages.

    Follicular phase (preparing for ovulation) 

    During the follicular phase of the cycle, the increased levels of estrogen and the low levels of progesterone may improve the skin’s appearance. Improved mood is also associated with this phase.  

    What happens to hormones

    High levels of FSH in the early follicular phase stimulate folliculogenesis (growth and maturation of follicles). In the beginning of the cycle, many follicles grow equally quickly until a dominant follicle emerges. 

    Maturing follicles produce estrogen, which causes the luteinizing hormone to increase. High levels of estrogen and LH activate the complex biochemical interactions that lead to ovulation. 

    Estrogen is one of the most impactful hormones in the body. Estrogen is responsible for the stimulation of secondary female characteristics (body composition, breast development, menstrual cycle, etc.). It can also impact other aspects of health such as mood stability, complexion, bone health, and cholesterol levels.

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    How the follicular phase might feel

    Many people report a positive mood between days 6 and 14 of their cycle. For some, their confidence grows slightly between days 6 and 13 of their cycle due to increased estrogen and testosterone levels. If you notice this is true for you, you can plan your schedule so you’re feeling your most confident during meetings or job interviews. 

    Hormone levels on days 6–14 of the cycle can affect the skin’s scent, which can affect how fragrances and perfumes interact with each persons’ personal chemistry. 


    Ovulation is when an egg is released from the dominant follicle and waits to be fertilized in a uterine tube. For a regular 28-day cycle, the greatest chances of conception occur around 14 days before the next menstrual cycle begins. However, sperm can survive in the uterus for about five days, and a released egg lives for about 24 hours, so conception is possible at any point during this period of time, which is called the fertile window.

    What happens to hormones

    When estrogen levels peak, it also causes the luteinizing hormone level to rise. This process kicks off ovulation and causes the egg to be released from the dominant follicle.

    How ovulation might feel

    Ovulation is generally regular without any extra symptoms aside from changes in vaginal secretion. Cervical mucus increases in quantity and becomes clear and stretchy, like egg whites, during this phase.

    Different types of vaginal discharge occur throughout the cycle, so discharge that slightly changes color and consistency may be normal. During ovulation, there may be mild soreness on the side of the body where the ovary is releasing an egg. This is called mittelschmerz (German for “middle pain”) and can last from a few minutes to one to two days. Mittelschmerz is completely normal, and it’s also normal not to experience it.

    However, if there’s a sharp pain in the belly during ovulation or an excessive amount of discharge, it’s possible that there are underlying health issues that need medical treatment.

    Luteal phase

    After ovulation, LH and estrogen levels drop. The dominant follicle transforms into the corpus luteum, which is a sort of temporary organ that predominantly secretes progesterone to prepare the uterine lining for implantation of a fertilized egg.

    This phase lasts for 14 days for most people.

    What happens to hormones

    During the luteal phase, the body is preparing for the implantation of a fertilized egg. Progesterone, which dominates during the luteal phase, starts to increase. Meanwhile, estrogen levels drop after ovulation but then slowly rise, along with progesterone. If conception didn’t happen, both progesterone and estrogen levels start lowering after their peak around days 22–24 of the cycle, which can start the onset of premenstrual syndrome (PMS). Many people feel slightly off or unwell during the luteal phase.

    The hormonal fluctuations during the second part of luteal phase may cause irritability, negative mood, or skin issues. A mid-luteal spike in progesterone can cause constipation because progesterone relaxes smooth muscles, including the bowels.

    How the luteal phase might feel

    Common symptoms of the second part of the luteal phase include all of the known symptoms of PMS, such as:

    • Increased appetite
    • Tiredness
    • Acne
    • Fatigue
    • Oily hair and skin

    For people who experience PMS, the second part of the luteal phase may bring discomfort and interfere with daily life. Learning how to relieve PMS symptoms can provide an increased understanding of the body and help get you through the luteal phase with minimal discomfort.


    In the absence of a pregnancy, hormone levels start to decrease, and prostaglandin levels rise in the later part of the luteal phase. These changes cause the uterine muscles to contract, and the inner lining of the uterus (endometrium) is shed. This is menstruation, or your period, which is the beginning of the monthly cycle.

    Periods that last anywhere from two to seven days are considered normal.

    What happens to hormones

    Since conception didn’t occur, progesterone and estrogen start to decrease. Some common menstrual symptoms include cramping, tenderness of the skin and breasts, sudden mood swings, tiredness, headaches and migraines, and lower back pain.

    How menstruation might feel

    Many people feel uncomfortable, tired, and have a negative mood during menstruation. Fortunately, there are lots of medicines and foods that can help with this.

    Some people who have intense cramps during their period often use pain-relieving medication. Others apply heating pads on their lower back and abdomen to ease cramping pains.

    Your period might last longer than average or be more intense. This is typically nothing to worry about, but it’s a good idea to talk to a health care provider about it to confirm that there aren’t any health issues affecting your periods. Dietary changes can help compensate for the loss of nutrients from heavy bleeding.

    Understanding the monthly cycle can improve symptoms

    Here’s how to improve symptoms by getting to know the menstrual cycle.

    • Tracking cycles using a calendar can help some people better anticipate symptoms.
    • Noting personal observations on a calendar can show which diet, skin care, and other changes have an effect on symptoms.
    • Changes in blood glucose levels and insulin resistance due to fluctuations of progesterone can affect appetite. Knowing how hormonal changes affect insulin and tracking your appetite changes and cravings can help you monitor your health.

    Menstrual cycle: frequently asked questions

    Here are the answers to the most common questions that Flo users have about their monthly cycle.

    When are you most likely to get pregnant?

    Certain days of the month come with higher chances of conception.

    It’s possible to get pregnant at any point in the menstrual cycle.

    Because sperm can survive up to five days inside the uterus, sex without birth control could lead to pregnancy at any time of the month, since regular cycles can shift unpredictably.

    However, the general rule is that the highest chances of getting pregnant are during the days leading up to and including ovulation — the fertile window. Tracking ovulation and the fertile window is especially important for people who are trying to get pregnant via in-vitro fertilization or who are treating infertility.

    When can you have sex?

    It's up to you how to navigate sex and your period. You can have sex whenever you want on any day of your menstrual cycle. The reproductive organs are more susceptible to infection during menstruation.

    • Scheduling fewer activities during menstruation can help when your energy is low.
    • Some people schedule trips and vacations around their cycle.
    • Pap smears are most accurate if they’re performed when you’re not on your period. Make sure to avoid douching, sexual intercourse, and using vaginal medications or hygiene products such as creams or gels for two days before the appointment.
    • When estrogen levels are high (before ovulation and in the middle of the luteal phase), the body has its highest tolerance for pain, making this a good time to schedule appointments like waxing, getting a tattoo, or visiting the dentist.

    Bottom line

    If you’re experiencing severe symptoms due to hormonal changes, make sure to talk to a health care provider, who can run necessary tests. Because hormone imbalances can be caused by more serious conditions, it’s important to see a health care provider if you have any concerns. 

    Understanding how hormone levels change during the menstrual cycle can help you adjust your routines and optimize your life. A couple of minor lifestyle changes and calendar notes can really make a difference, so consider tracking your cycle to make the most of each month!


    “Ovulation Pain.” NHS Choices, NHS, 2 Aug. 2019,

    Mayo Clinic Staff. “Menstrual Cycle: What's Normal, What's Not.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 13 June 2019,

    Reed, Beverly G, and Bruce R Carr. “The Normal Menstrual Cycle and the Control of Ovulation.” Endotext [Internet]., U.S. National Library of Medicine, 5 Aug. 2018,

    History of updates

    Current version (15 November 2023)

    Reviewed by Andrei Marhol, PhD, Flo lead medical advisor, Lithuania

    Published (26 November 2018)

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