Menstrual cycles. We have about 400 of them in our lifetime. Yet most of us know so little about how this amazing process really works, and why they’re so important to pay attention to and know how to interpret. It’s led most of us to grow up pretty much in the dark about a fact of life that if you have a uterus, you’re going to experience for 35 to 40 or so years of your life. That right there's a good reason to know more about how your menstrual cycle works.
But there is more: we now know that our menstrual cycles are one of the most important signs we have as women about our health. Its characteristics – such as our regularity, the amount of flow, and whether or not we’re ovulating – can indicate not just our hormonal health, but can tell us a great deal about whether we have underlying inflammation, microbiome disruption, oxidative stress, nutritional insufficiencies, and other root imbalances that can have a bigger impact on our total – and long-term – well being. As such, it’s recognized in medicine as our 6th vital sign, as vital as your pulse or body temperature, and one of the most powerful indicators of the state of our health and well-being. And that’s why I want to make sure you know your personal cycle! It’s a powerful ticket on a journey to understanding your body, hormones, and wellness at the deepest levels.
This stuff is so important that I dedicated two chapters of my new book, Hormone Intelligence, to helping all women gain a deeper understanding of the language of our cycles and hormones. I’d love to take you on a journey into the very important foundational basics of how your menstrual cycle works. I started paying attention to my own cycle when I was 15 years old, and now, 40 years later, I can say that knowledge has been far more valuable than a lot of what I learned in school! In fact, I hope you’ll share this with the young women in your life, but this information is so powerful and valuable at any age, even if you’re not cycling anymore, because the health of our cycles at any age sets the stage for our health at the next stage.
What Is a Menstrual Cycle, Anyway?
First, let’s clarify a common misconception that the term “menstrual cycle” only describes the days when you’re on your period. Your menstrual cycle actually includes your period, but also encompasses the entire length of time between the first day of your period and the last day before your next period starts.
From a simple biological point of view, your menstrual cycle is the process your body goes through each month to prepare for a potential pregnancy. It involves hormonal fluctuations, the development and release of an egg from the ovaries (ovulation), and changes to the endometrium (the lining of the uterus) all of which are part of this preparation. But it’s also so much more. It’s the rhythm that guides our lives, moods, energy, desires, cravings, attractions, inspirations, and so much of what makes us – us. It’s also not just something that happens in your reproductive organs – your whole body is involved!
Your Cycle, Your Endocrine System
From your hypothalamus and pituitary glands in your brain, to your thyroid and adrenal glands, your menstrual cycle is a full-on hormonal (endocrine) affair!
These are the glands that regulate your menstrual cycle:
- The ovaries, which is where your eggs (ova) form prior to ovulation
- The ovarian follicles. Human eggs are stored in their own individual sacs called (ovarian) follicles. Each cycle, a group of selected follicles mature. When an egg is ovulated, it leaves its follicle behind.
- Your brain, specifically the hypothalamus, which releases gonadotropin releasing hormone (GnRH) and the pituitary, which releases luteinizing hormone and follicle stimulating hormone
- Your thyroid, which not only controls metabolism, but also is involved in menstrual cycle regularity and function
- Your adrenal glands, which produce androgens and progesterone
There are also quite a few different hormones playing a role in your monthly cycle. Let me introduce you to them!
- Estrogen: The “Queen Bee” hormone. Without getting too deep in the weeds, a woman’s body produces 3 types of estrogen but estradiol (E2) is the key hormone that majorly influences your development into a woman and your menstrual cycle. It drives the first half of your cycle, helping to build the uterine lining, and helps cue the start of your period to start (unless the egg is fertilized and pregnancy occurs).
- Progesterone: The hormone that dominates the second half of your cycle. Progesterone helps stabilize the uterine lining, prepares for and supports the body if pregnancy occurs, or helps cue the start of your period with estrogen.
- Luteinizing hormone (LH): The driving hormone behind ovulation. LH stimulates the ovarian follicles to produce estrogen, causes the ovarian follicle to release the mature egg, and in the second half of the cycle, and stimulates the corpus luteum (a mass of cells produced in the ovary) to produce progesterone.
- Follicle stimulating hormone (FSH): The primary hormone responsible for the growth of ovarian follicles. These follicles develop before ovulation and contain the developing egg. FSH also increases estrogen production.
- Androgens: While we think of common androgens, like testosterone, as primarily male hormones, they’re actually produced in your adrenal glands and ovaries. They are also used by your follicles to create estrogen and progesterone that are necessary in adequate levels for a healthy cycle.
All of these hormones fluctuate at different times throughout the month to create the orchestra that is your monthly menstrual cycle, which can be broken down into four distinct phases.
A Healthy Menstrual Cycle
The menstrual cycle is divided into two main phases: the follicular phase and the luteal phase. Within those two phases, it can be divided further to include separate phases for menstruation and ovulation (as you’ll learn about below.) Each of these phases has its own unique characteristics, including hormonal shifts, physiological changes, and physical signs and symptoms. In this article/podcast I talk about interesting changes that accompany these phases that you can use as a subtle inner guidance system, that when you learn to work with, you can really use to your advantage in terms of your diet, workouts, sex life, and even spending, saving, and career moves!
The descriptions below are based on a classic 28-day cycle, but check it out: there’s no such thing as a perfect cycle and what’s considered “normal” can vary by age and based on other factors, such as stopping the Pill. That said, there is a basic set of rules about what’s considered typical and what’s cause for concern. In a nutshell, when everything is flowing smoothly and you’re experiencing a predictable rise and fall of hormones, you shouldn’t have any majorly troublesome symptoms, like drastic mood swings, debilitating cramps, or heavy bleeding that keeps you from wanting to leave the house.
A healthy, normal menstrual cycle falls within these parameters:
- Cycle length: 26 to 34 days (except during perimenopause, when they might be longer or shorter)
- Period length: 3 to 7 days
- Amount of bleeding: No more than 6 pads or tampons per day
- Blood color: It’s normal for period blood color to vary – from very dark blood (older blood being shed) to bright red blood (fresh blood.) The color changes when it gets exposed to air. If your period blood is very pale or light pink and watery, it could be a sign that you have low iron (anemia) and that’s worth having checked by a simple blood test because it can also make you feel very tired.
- Cervical mucus: Also sometimes called cervical fluid, cervical mucus is normal liquid produced by your cervix during the course of the menstrual cycle. The amount of fluid produced varies from person to person but also over the course of the cycle. The week or so leading up to ovulation, cervical mucus becomes clear, watery, and stretchy and can look like egg whites. Early in the cycle and after ovulation, cervical mucus becomes thicker and less-clear.
- Blood clots: Small clots, considered less than the size of a quarter in diameter and just on occasion, are normal. Larger clots, or frequent or regular clotting with your periods can be a sign of hormone imbalance.
- Pain: Pain throughout your cycle shouldn’t be more than occasional mild cramps or pelvic tension. You should not need days of pain relievers, hot water bottles, or other comfort measures for cramps. When it comes to breast pain, you may experience breast “fullness’” but breast pain, cysts, or cyclic lumps are not standard. Premenstrual headaches and migraines are common, but they are not considered “normal.”
- Mood and PMS: Mild shifts in mood, level of desire for social connection, energy, sleep, and cravings are normal; but these should not feel extreme, disruptive, or out of control.
- Ovulation discomfort, also called mittelschmerz (German for “middle pain”) is a mild pain that some people feel in the lower abdomen around the time of ovulation.
When it comes to the exact length, timing of ovulation, and hormonal shifts and symptoms, it’s more important to establish your “normal” and then not sweat any small shifts or changes. That said, if you notice sudden changes to your cycle length or bleeding that don’t seem to have an obvious explanation, it may mean you have a deeper hormonal imbalance going on. That’s a good time to talk with a midwife, nurse practitioner, or medical practitioner you trust. My book Hormone Intelligence can also help you as you sort out what might be going on, and may be able to help you restore cycle balance.
Your Menstrual Cycle in Four Phases
Menstruation aka Your Period (~ Days 1 – 6)
You might be surprised that I’m starting with menstruation – after all, isn’t that the END of the menstrual cycle? Actually, technically, it’s the start! I think of it as shedding the old (uterine lining, that is) and starting fresh (I do honor that this might feel far from something to celebrate if you’re trying to get pregnant…but hopefully it’s a time for you to start new, too).
Your period occurs when your uterine lining sheds due to the drop in estrogen and progesterone that happens if conception doesn’t occur. This drop in hormone levels is also, in part, responsible for many of the common symptoms and discomforts you might experience in the days leading up to your period. But other things are going on, too, that lead to premenstrual and early period day symptoms like cramps and loose stools, particularly, increased production of an inflammatory chemical called prostaglandin. But overall, a healthy period is 3-7 days long, and while it may bring some mild discomforts, it shouldn’t be painful enough to require medication, or so heavy that you’re blowing through more than 6 pads or tampons a day, which I talk about here.
The couple of days prior to and the first couple of days of our period are the energy low point of the month for most women, so give yourself a pass – this is normal. Shifts in our brainwaves during this time may make you crave quiet, alone time, and some R&R. You may find that you’re in a creative ”zone” ripe for journaling or artistic expression. It’s a great time to give yourself permission to pause, slow down, and rest if you feel you need it. I think of this as a time of shedding layers – which is what your body is actually doing – so do what you can to let go of anything you need to let go of, whether emotionally, spiritually, physically, to give yourself a metaphorical new start.
The Follicular Phase (~ Days 1 – 13, includes the menstrual phase)
The follicular phase starts on the first day of your cycle (as in the first day of your period, so yes, they overlap) and ends at ovulation. It’s named for the follicles that are maturing in your ovaries and is the estrogen dominant time of the cycle. During this phase, the uterine lining sheds and then starts proliferating, getting thicker, lusher, and ready for implantation if the egg that is released happens to be fertilized. During the follicular phase, estrogen is dominant and testosterone and FSH start to rise.
Peaking estrogen levels leads to a welcome calm and optimistic headspace, while a higher level of testosterone enhances energy, confidence, motivation and as well as muscle strength and sex drive. We thrive on socializing and our hormones make us not only feel great but give us clearer skin and more symmetrical features – we actually look prettier and sexier to ourselves! We tend to feel more inclined to go out with girlfriends, say yes to a gathering, and go out “on the town.” Studies show a keener ability for recognizing facial expressions and more empathy as a result in this cycle phase.
Ovulation (~ Days 14 – 18)
Ovulation marks the beginning of the luteal phase and usually occurs mid-cycle. It starts with a surge of luteinizing hormone that causes the mature follicle to rupture and release the ovum, which travels down the fallopian tube and either meets up with sperm trying to find that egg to fertilize it, or it passes on down into the uterus after about five days, unfertilized. The egg survives for fertilization for only about 24 hours, but because viable sperm can be lurking in there for 3-5 days, each month we ovulate we have a fertile window of potentially that length of time. The most fertile period is from about five days before until 1 to 2 days after ovulation.
Estrogen starts to increase toward its second peak, along with an increase in testosterone, while progesterone really takes over the landscape, being produced by the corpus luteum, the divot in the ovaries where the egg was released from and becoming dominant in the second half of the cycle.
Knowing when you’re ovulating is really important – it can help you prevent an unwanted pregnancy, time conception if you want to get pregnant, and if you’re not ovulating, this can be a sign of stress, hormonal problems, including PCOS. You know you’re ovulating (and fertile) when your vaginal discharge becomes plentiful, clear and stretchy, with a texture that is usually described as being like egg whites.
This copious, odorless, cervical mucus is specifically ”engineered” to have the perfect pH to keep sperm alive for about 5 days, help healthy sperm find their way to your cervix, while “weeding out” damaged ones as a way to protect your egg from a sperm with possible bad DNA, transforming the sperm as they pass through your cervix so they have more of a chance of fertilizing that waiting egg, and it also makes for great vaginal lubrication. Some women experience “Mittelshmerz” sign – a sharp pain in either your right or left side – depending on which ovary is releasing the egg that month.
High estrogen and testosterone levels boost sexual desires and pleasure way up – it’s the time of month that it’s easiest to experience orgasm, including that toe-curling kind. It’s nature’s sneaky way of trying to get us to reproduce. We unconsciously turn the flame way up, and potential mates are like moths.
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The Luteal Phase (Days 14 through 28, includes ovulation)
The luteal phase is the second half of your menstrual cycle, between when you ovulate and when you get your period. It’s named after the corpus luteum and is the progesterone dominant time of the cycle. If fertilization of the ovum occurs after ovulation, the fertilized egg will travel through your fallopian tube to your uterine lining where it will implant and grow. If fertilization does not occur, progesterone and estrogen levels will drop about ten days after ovulation, leading your uterine lining to shed – which is the start of your next period.
In the first half of the luteal phase, especially just after ovulation, cervical mucus is still copious, your energy high, and your sex drive ramped up. Around midway in the luteal phase, after the peak in progesterone and the second smaller bump in estrogen start to decline, about a week before your period, your cervical mucus will start to become more sparse, thicker, whiter, and more “tacky” or pasty. In this form, it’s more hostile to sperm, actually preventing them from making their way toward your uterus, which is now past its peak for optimal implantation of an embryo. Cervical mucus cyclicity is an important indication of hormonal health; low estrogen will prevent cervical mucus production, and lack of ovulation is an indication of low progesterone and carries health risks as discussed above.
Also in the second half of your luteal phase,, especially as you head into those 5 or so days before your next period is due, your body starts to produce more of a chemical called prostaglandin, which increases inflammation, produces uterine cramping, increases your overall sense of pain, and also gets your bowels a bit irritated – leading to some bloating and for many women, looser poops (a happy thing for women who tend to be constipated, but not happy for everyone else who experiences this). The more inflammation you already have, the more prostaglandins you’ll produce – and the more pain, etc.
Declining estrogen levels at this time can also lead to lower moods, lower energy, and a feeling of being “depleted.” You may want to turn your focus inwards – rest, nest, and journal over socialization and partying. We may also feel more easily irritated and emotionally reactive. It’s thought that during this time our immune function becomes a little bit suppressed so that we don’t react with hostility to sperm or an embryo if we conceive so you might notice that you tend to get sick with a cold or infection right before your period. And further, due to fluctuations in prostaglandins and estrogen that if you have it, you’re more likely to experience an asthma exacerbation. So it’s important to build in some time for quiet and self-care, which can pre-empt irritability, resentment, and burn-out, as well as getting sick, if you try to push against what your natural inclination is – which is to be more restful.
Menstrual Cycles from Puberty Through Menopause
Our menstrual cycles shift patterns quite a bit depending on our age. Here’s a 30,000 foot view of what that looks like:
Puberty: Optimally begins between 11 and 15 years old, may be accompanied by some mood changes, irregular cycles, and light cramps but should not cause pain, acne, depression, anxiety or other severe symptoms. Menstrual cycle length: commonly irregular for the first few years after puberty, then averages every 26-34 days, then might start to get irregular again in your 40s.
Reproductive Years: From our early 20s to our early mid-40s, healthy menstrual cycles are typically every 26-34 days, mostly regular other than in times of stress or illness, or postpartum. Bleeding is often heavier on the first 2 days, and many women experience common signs premenstrually including pelvic fullness or heaviness, increased craving for carbs, breast fullness, and some water retention; but these should be mild and easy to manage without medication or anything beyond simple self care.
Perimenopause: Naturally begins in your early-mid 40s and can last as long as 8 years before menopause (complete cessation of ovulation and menstruation, international average age is 52). Periods often become slightly irregular, you may have longer or shorter, lighter or heavier periods, and as you get closer to menopause, you may notice some mild hot flashes, sleep changes, and changes in your sex drive. But again, disruption, discomfort, or extreme symptoms represent hormone imbalance.
How to Get to Know Your Menstrual Cycle
Taking small steps to get to know how your menstrual cycle works can feel overwhelming. Where do you start? Here are some simple strategies to get you started:
- Keep a menstrual cycle chart: Start tracking your cycle using a chart, calendar, or app. Notice if your period length, flow, any symptoms, and its regularity month-to-month.
- Check out your fertile mucus. You know you’re ovulating (and fertile) when your vaginal discharge becomes plentiful, clear, and stretchy, with a texture that is usually described as being like egg whites.
- Take your temperature: Right after ovulation, your BBT increases approximately 0.5 to 1 degree Fahrenheit and remains at this new temperature until right before your next period. This can be a way to confirm ovulation if you’re not sure. Take your temperature first thing in the morning before you get out of bed.
- Pay attention to how you feel. Don’t just track your cycle; begin to notice shifts in how you feel physically, mentally, energetically, and emotionally. Journaling can help you actively set aside time to pause and really tap into your body.
Learning to track my cycle as a teenager was one of the most important steps I took toward body knowledge and empowerment and it’s something I want every woman to understand and feel ownership of for self-awareness and also health literacy.
When it Comes to Your Cycle, Knowledge is Power
While hormones are a force of nature and we can't control it all, the more you know about your own hormones and how your menstrual cycle works, the more you can live in harmony with – and even influence what’s happening below the surface. As you begin to recognize the shifts that occur at different phases of our cycle, I hope you will also naturally start to marvel at and celebrate some of these changes as they occur. And if your cycles have been causing you trouble, now you have a roadmap to tell you when they’re getting back on track.
Barbieri RL. The endocrinology of the menstrual cycle. InHuman Fertility 2014 (pp. 145-169). Humana Press, New York, NY.
Brodin T, et al. Menstrual cycle length is an age-independent marker of female fertility: results from 6271 treatment cycles of in vitro fertilization. Fertil Steril. 2008 Nov;90(5):1656-61.
Fehring RJ, Schneider M, Raviele K. Variability in the phases of the menstrual cycle. Journal of Obstetric, Gynecologic & Neonatal Nursing. 2006 May 1;35(3):376-84.
Gunn DL, Jenkin PM, Gunn AL. Menstrual periodicity; statistical observations on a large sample of normal cases. BJOG: An International Journal of Obstetrics & Gynaecology. 1937 Oct;44(5):839-79.
Solomon C,, et al.: Long or highly irregular menstrual cycles as a marker for risk of type 2 diabetes mellitus, JAMA. 286(19):2001; 2421–2426.
Treloar AE, Boynton RE, Behn BG, Brown BW. Variation of the human menstrual cycle through reproductive life. International journal of fertility. 1967;12(1 Pt 2):77-126.
Vitzthum V. The Ecology and Evolutionary Endocrinology of Reproduction in the Human Female. YEARBOOK OF PHYSICAL ANTHROPOLOGY 52:95–136 (2009).: 95-136.