What is normal and what is not?
A woman’s menstrual cycle (period cycle) tells us a lot about her health, fertility, and overall well-being.
Proper monitoring and understanding of both the cycle and its irregularities are important guides for women in maintaining their reproductive health.
When did your last menstrual period start, or how long did it last?
Tracking your menstrual cycles helps you understand what is normal for you, accurately measure your ovulation, and identify important changes — such as a missed period or unexpected uterine bleeding. While menstrual cycle irregularities are usually not serious, they can sometimes signal potential future health concerns.
What is the menstrual cycle?
Each month, one of the ovaries alternately releases an egg through the process of ovulation. At the same time, monthly hormonal changes prepare the uterus for a possible pregnancy. When ovulation occurs around the 14th day of the cycle, and the egg is not fertilized, the endometrium sheds from the uterus through the vagina, causing a bleeding that typically lasts 4–5 days. This is the menstrual period.
What is normal?
The menstrual cycle, which is counted from the first day of one period to the first day of the next, is not the same for every woman. A menstrual period may occur every 21 to 35 days and last from two to seven days. In the early years after a woman first begins menstruating, long cycles are very common. However, menstrual cycles tend to become more organized and more regular as a woman gets older. Your menstrual cycle may be regular — with roughly the same length every month — or somewhat irregular. Your period may be light or heavy, painful or painless, long in duration or relatively short, and still be considered completely normal. In a broad sense, “normal” is whatever is normal for you personally and individually.
It is very important to keep in mind that some types of contraception, such as contraceptive pills and intrauterine devices (IUDs), may change your menstrual cycle.
As you approach menopause, your cycle may become irregular again. However, because the risk of uterine cancer increases with age, discuss any irregular bleeding (metrorrhagia) that occurs during menopause.
How can I track my menstrual cycle?
To understand what is normal for you, start keeping a record of your menstrual cycle in a calendar.
Begin by tracking the start date each month for several consecutive months to determine how regular your periods are. If you are concerned about your period, also note the following each month:
- Start and end dates.
- How long does your period usually last?
- Is it longer or shorter than usual?
- Flow. Record the heaviness of your flow. Does it seem lighter or heavier than usual? How often do you need to change your sanitary protection?
- Are any clots present?
- Abnormal bleeding. Do you experience bleeding between periods?
- Pain. Describe any pain related to your period. Is it worse than usual?
- Other changes. Have you noticed changes in mood or behavior?
- Did anything new occur during this menstrual cycle?
What causes menstrual cycle irregularities?
Irregularities and disruptions in the menstrual cycle can have many different causes, including:
Pregnancy or breastfeeding. A missed period can be an early sign of pregnancy. Breastfeeding almost always delays the return of menstruation after pregnancy.
Eating disorders, excessive weight loss, or excessive exercise. Eating disorders — such as anorexia nervosa — significant weight loss, and high levels of physical activity can disrupt menstruation.
Polycystic ovary syndrome (PCOS). Women with this endocrine disorder may have irregular periods as well as enlarged ovaries containing small fluid-filled follicles that appear as tiny cysts on each ovary during a gynecological ultrasound.
Premature ovarian insufficiency. Premature ovarian insufficiency refers to the loss of normal ovarian function before age 40. Women with this condition — also known as primary ovarian insufficiency — may have irregular or occasional periods for years.
Pelvic inflammatory disease (PID). This infection of the reproductive organs can certainly cause irregular menstruation.
Uterine fibroids. uterine fibroids can cause heavy menstrual bleeding as well as prolonged menstrual periods.
What can I do to prevent menstrual disorders?
For some women, the use of birth control pills can help regulate their cycles. Treating any underlying issues, such as an eating disorder, can also be beneficial. However, certain menstrual disorders cannot be prevented.
Additionally, consult your gynecologist if:
Your periods suddenly stop for more than 90 days, and you are confirmed not to be pregnant.
Your periods become irregular after having been consistently regular.
You bleed continuously for more than seven days.
You bleed more heavily than usual, or you need to change your pad or tampon more than once every two hours.
Your periods occur less than 21 days apart or more than 35 days apart.
You experience bleeding between periods.
You have very severe pain during your period.
You suddenly develop a fever and feel unwell after using a tampon.
If you have questions or concerns about your menstrual cycle, speak with your gynecologist promptly.
The days before menstruation are often accompanied by period symptoms, and if your period is late, see the causes of a late period.
The phases of the menstrual cycle, day by day
The cycle is not just your period. It is an ongoing hormonal “conversation” between the brain and the ovaries, divided into phases that follow a clear order. The information below refers to a typical 28-day cycle. In longer or shorter cycles, it is mainly the length of the first phase that changes.
Menstruation (roughly days 1 to 5)
Estrogen and progesterone are at their lowest point. The endometrium is shed. Already during these days, the pituitary gland raises FSH and a group of follicles starts to grow.
Follicular phase (from day 1 to ovulation)
One follicle becomes dominant and produces more and more estradiol. The endometrium thickens again. This is the phase with the greatest variation: in some women it lasts 10 days, in others three weeks. That is why ovulation does not always fall on day 14.
Ovulation (around the middle of the cycle)
When estradiol reaches a high level, it triggers a sharp surge of LH. About 24 to 36 hours later, the egg is released and can be fertilized for about 12 to 24 hours. More about ovulation and its signs.
Luteal phase (from ovulation to the next period)
The empty follicle turns into the corpus luteum and produces progesterone, which stabilizes the endometrium for possible implantation. This phase lasts a fairly constant 12 to 14 days. If no pregnancy occurs, the corpus luteum breaks down, hormone levels fall and a new period begins.
Body signs in each phase
Your body gives clues about where you are in your cycle. With a little observation you can learn to recognize them:
- Cervical mucus: after your period it is scant or thick. Close to ovulation it becomes abundant, clear and stretchy, like raw egg white. After ovulation it thickens again.
- Basal body temperature: measured every morning before you get up, it rises by about 0.2 to 0.5 degrees after ovulation because of progesterone. It confirms that ovulation has happened, but it does not predict it.
- Ovulation tests: they detect the rise of LH in urine and show that ovulation is approaching within the next few days.
- Breasts and mood: breast tenderness, bloating and mood changes usually appear in the luteal phase.
If you are trying to conceive, combining mucus observation with LH tests is usually more useful than apps that calculate based on dates alone. Read more in our guide on how to get pregnant.
The menstrual cycle at every age
Puberty
In the first years after the first period, many cycles occur without ovulation, which is why they are often irregular. Cycles of up to 45 days may be considered acceptable in the first year. They usually settle within two to three years.
Reproductive years
From about age 20 to 40, the cycle is usually at its most regular. Small differences of a few days from month to month are normal. After 35, many women notice that their cycle gradually becomes a little shorter.
The transition to menopause
Usually after 40, the ovarian reserve declines, hormones fluctuate and cycles become shorter or further apart, often with changes in flow. This phase is described in detail in our guide to perimenopause.
The cycle as an indicator of overall health
International scientific bodies, such as the American College of Obstetricians and Gynecologists, describe the menstrual cycle as a “vital sign,” like blood pressure or pulse. The reason is simple: a regular cycle shows that the brain, thyroid, ovaries and metabolism are working together properly.
When your cycle changes for no obvious reason, it may be the first sign of:
- a thyroid disorder or elevated prolactin
- insulin resistance, which often accompanies polycystic ovaries
- inadequate nutrition or overtraining
- iron deficiency anemia, when periods are very heavy
Cycles without ovulation
Bleeding does not always mean that ovulation has occurred. In an anovulatory cycle, the endometrium is exposed only to estrogen, without the protective effect of progesterone. It sheds irregularly, with bleeding that may come earlier, later or be heavier.
An occasional cycle like this is normal, especially in adolescence and after 40. When it keeps happening over a long period, however, it makes conception harder and raises the long-term risk of endometrial hyperplasia. Measuring progesterone about seven days before your expected period shows whether ovulation took place.
Cycle tracking apps: what they can and cannot do
Apps make tracking easy, and that is their biggest advantage. They do have limits, though:
- Most of them estimate your fertile days from the average of your previous cycles. If your cycle varies from month to month, the prediction loses accuracy.
- They are not a reliable method of contraception when they rely on dates alone.
- They become more useful when you also give them other data, such as temperature or LH test results.
Their greatest value is the history they build up. Show it to your doctor at your next appointment.
How to measure your cycle length correctly
A common mistake is to count from the end of your period. Day one of the cycle is the first day of actual bleeding, not any spotting that may come before it. The cycle ends on the day before your next period starts.
To draw any conclusion, you need at least three to six cycles. Work out the shortest and the longest. If the difference between them stays under about seven days, your cycle is considered regular, even if it is never exactly 28 days.
For a personalized assessment of your case, book an appointment with Dr. Panagiotis Polyzos at his office in Athens or Volos.
Frequently Asked Questions
How many days does a normal cycle last?
From 21 to 35 days in adult women, counting from the first day of one period to the first day of the next. The period itself lasts 2 to 7 days.
What are the phases of the cycle?
Menstruation, the follicular phase, ovulation and the luteal phase. The luteal phase lasts a fairly constant 14 days or so, while the follicular phase varies.
When are the fertile days?
The five days before ovulation and the day of ovulation itself. In a 28-day cycle, this means roughly day 9 to day 14. See how to calculate your fertile days.
When is a cycle considered irregular?
When it lasts less than 21 or more than 35 days, when its length varies by more than 7 to 9 days from month to month, or when periods are missed. Read more about a late period.
How do I track my cycle?
Note in a diary or app the first day of each period, how long it lasts, how heavy it is and any symptoms. Three to six months of records give your doctor a valuable picture.
Does ovulation always happen on day 14 of the cycle?
No. Day 14 only applies to a typical 28-day cycle. Because the luteal phase lasts a fairly constant 14 days or so, in a 35-day cycle ovulation happens around day 21, while in a 24-day cycle it happens around day 10.
Can I have a period without ovulating?
Yes. In cycles without ovulation, bleeding is caused by fluctuating estrogen and is usually more irregular in timing and amount. This is common in adolescence and before menopause, but when it keeps happening at other ages, it needs to be checked.
Which hormones do we measure to check the cycle?
Usually FSH, LH and estradiol in the first days of the period, progesterone about one week before the expected period, as well as TSH and prolactin. AMH gives a picture of the ovarian reserve and can be measured on any day.
Does the cycle affect mood and energy?
Many women report more energy in the first half of the cycle and more fatigue or sensitivity in the days before their period, because of hormonal fluctuations. The intensity varies a lot from woman to woman. When symptoms are severe, discuss them with your doctor.
