Menstruation: symptoms and characteristics of the monthly period

By (gynecologist), (gynecologist), (embryologist), (embryologist) and (biochemist).
Last Update: 10/18/2023

Menstruation is the vaginal bleeding that occurs at the beginning of a woman's menstrual cycle and corresponds to the shedding of the endometrium when there has been no pregnancy.

This stage of the menstrual cycle is also known as a period since it has a periodicity, that is, it is a cyclical process that is repeated every month.

Despite this, menstruation may vary from cycle to cycle in each woman in terms of the amount, appearance, and duration of bleeding, and may manifest differently in each woman.

What is a period?

The typical menstrual bleeding is a mixture of vaginal discharge, blood, and endometrial tissue. Its duration is usually 3 to 5 days, in which an approximate quantity of 40-50 ml is expelled.

However, there are women with very short and light perioda, and others with more abundant bleeding that can last up to 7 days.

From puberty until menopause, a woman's body is prepared every month for a possible pregnancy. Specifically, it is the inner layer of the uterus, called the endometrium, that is renewed in each menstrual cycle to house the embryo once fertilized, and be able to give rise to pregnancy.

If neither fertilization nor implantation of the embryo occurs, the endometrium detaches and menstruation occurs.

Furthermore, the start of the period means the beginning of a new menstrual cycle, as it corresponds to the signal to start the synthesis of sex hormones again and allow the maturation of a new follicle in the ovary.

Phases of the menstrual cycle

The menstrual cycle lasts approximately 28 days, that is, every 28 days a woman will experience the menstrual bleeding typical of her period. However, there are women with longer or shorter cycles, which is completely normal.

During the menstrual cycle, the following stages are differentiated according to the levels of the female sex hormones, which are responsible for regulating the entire cycle:

the drop in estrogen and progesterone in a woman's body causes the endometrium lining the uterus to detach, which is then expelled as vaginal bleeding.
Follicular phase
Follicular development begins by the action of the hormone FSH in the ovaries. At the same time, estrogens synthesized in the ovaries ensure the proliferation of a new endometrium.
Ovulation phase
the rise of the LH hormone causes the mature follicle to rupture and an egg is released into the fallopian tube, a process known as ovulation.
Luteal phase
the corpus luteum formed in the ovary secretes progesterone, which acts on the endometrium causing it to reach the appropriate thickness and become receptive.

If you want to know more about each of these phases, we recommend that you read on: The Different Phases of the Menstrual Cycle.

What are the symptoms of menstruation?

The most characteristic symptom of the menstrual period is vaginal bleeding.

However, there are also other symptoms that a woman may feel when her period is due. These are discussed below:

  • Breast pain and swelling
  • Abdominal pain and cramping
  • Kidney pain
  • Headache
  • Acne
  • Mood swings
  • Fatigue
  • Gastrointestinal disturbances: nausea, gas, diarrhea, or constipation

It should be noted that some women suffer from a marked premenstrual syndrome, (PMS) with both emotional and physical symptoms appearing before the onset of menstruation.

To relieve these symptoms you can try, a healthy diet, drinking plenty of water, avoiding salt, reducing stress levels, and, if necessary, taking some painkillers.

Other characteristics

As we have said, menstruation is not the same in all women. Morever, the same woman may experience changes in her period throughout her reproductive life.

To continue, we are going to comment on some curiosities and characteristics of menstruation that all women should know.

First period

The first menstruation, known as menarche, and appears when girls reach puberty, around age 12 and 14. However, some girls have their first period at age 10 or it may be delayed until age 16.

During the first year, periods may be irregular, with little bleeding, since the body is still adapting to hormonal changes that act on the ovaries and endometrium.


Amenorrhea in the absence of menstruation, either at the onset of puberty or during some later stage in a woman's life.

The main cause of amenorrhea is pregnancy. Once a woman becomes pregnant, the endometrium does not shed and they do not menstruate until after giving birth.

Other causes of amenorrhea in women include the following:

  • Absence of uterus
  • Hormonal alterations: thyroid problems, PCOS, etc.
  • Sudden weight changes, anorexia, and obesity
  • Stress and anxiety
  • Infections: cystitis, viral process, etc.
  • Breastfeeding
  • Excessive physical activity
  • Some medications: antidepressants, immunosuppressants, etc.

Finally, the total cessation of menstruation occurs when a woman reaches menopause, at around the age of 50. If you want to read more on this subject, you can access the following article: What Is Menopause? – Age, Causes, Symptoms & Treatment.

Bleeding Colors

The color of menstrual bleeding depends on many factors, such as the flow or the day of menstruation a woman is on.

In general, the rule begins with a scarce flow of brown color. As the volume of bleeding increases, it takes on a more intense red color. Finally, during the last days of your period, the blood returns to a darker tone, and the flow decreases until it completely disappears.

Next, we will give a brief explanation of what each colour of bleeding can mean during menstruation:

Pale red
a light day of menstruation with little bleeding. It usually occurs when a woman takes the birth control pill, although it can also be a sign of a hormonal disorder.
Red orange
this color during menstruation is associated with infections. In this case, the blood will also have an unpleasant odor.
Bright red
is the usual color of menstruation on its most intense days.
Dark red
is the so-called old blood that usually appears during the last days of menstruation.
Brown or black
are the remnants of endometrial tissue in the blood. It may also be old blood from the last menstrual period.

If dark brown bleeding lasts for several days, it may indicate endometriosis, miscarriage, or benign tumor. Therefore, it would be advisable to see your doctor if there is any unusual bleeding.

Duration and quantity

As we have said, the days of menstruation and the amount of bleeding vary greatly from woman to woman, depending on many factors.

The only way to know if our menstruation has abnormal parameters is to pay attention to some characteristics such as the following:

  • Bleeding lasting more than 8 days
  • Bleeding that is very heavy and requires changing the pad or tampon more than every 4 hours
  • The menstrual cycle lasting less than 23 days, i.e., menstruation is repeated every 23 days or less
  • There is intermenstrual bleeding, which is known as metrorrhagia

If these alterations occur during the period each month, it is advisable to see a gynecologist.

FAQs from users

How do I distinguish implantaton bleeding from my period?

By Elena Izquierdo Trechera M.D., M.Sc. (gynecologist).

Post-implantation bleeding usually occurs a few days after the embryo transfer and is usually vaginal bleeding of a smaller amount than a menstrual period.

In case of unsuccessful treatment, menstruation occurs at least one week after the embryo transfer and the amount of bleeding is greater.

What is period for?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

During the menstrual cycle and thanks to the action of female sex hormones, ovarian follicles develop in the ovaries and the walls of the uterus (endometrium) become thick enough for an embryo to nest.

After ovulation, if there is no fertilization between egg and sperm or implantation of the embryo, the endometrium is shedded and eliminated in the form of menstruation. In this way, a new menstrual cycle can begin.

By Guillermo Quea Campos M.D. (gynecologist).

Many women have painful menstrual cycles, also called Dysmenorrhea, which is usually due to the contractions that the uterus produces for the detachment of the endometrium and its expulsion through the vagina.

There are two types of dysmenorrhea:

Primary dysmenorrhea
is the most common type and there is no associated cause. This type, as mentioned above, is due to contractions of the uterine musculature by an overproduction of substances called "Prostaglandins". This pain may begin one or two days before the menstrual period and usually has a very short duration. Primary dysmenorrhea usually begins in youth, just after the first menstruation (menarche) and becomes self-limiting as age advances and even disappears in some cases after the first childbirth.
Secondary dysmenorrhea
usually starts some years later and is caused by diseases affecting the uterus, such as endometriosis or uterine myomatosis. In addition, it is common for this pain to worsen over time. Secondary dysmenorrhea could be a cause of infertility depending on the underlying diagnosis.
Imagen: menstrual-pain-fertility-dysmenorrhea-faq

Can menstruation be affected by tubal ligation?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

No. Although the woman undergoes irreversible sterilization with tubal ligation, ovarian function and hormone levels are not altered. Ovulation also continues to take place, as well as the proliferation and desquamation of the endometrium in the absence of embryo implantation.

How can menstruation be distinguished from implantation bleeding?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

Implantation bleeding occurs when the embryo adheres to the uterine wall and causes a small wound in the endometrium, although this does not always take place.

Therefore, the implantation bleeding occurs a few days before the expected date of the period, i.e. when the embryo implantation takes place. Furthermore, the bleeding that takes place is much scarcer and lighter than that of menstruation.

What if the period is scanty and short on time?

By Marta Barranquero Gómez B.Sc., M.Sc. (embryologist).

Hypoamenorrhea, i.e., light menstruation does not have to mean anything bad. A lower than usual menstrual flow can be caused by changes in lifestyle habits, stressful situations or any other circumstance.

Menstruation is one of the secondary sexual characteristics that appear in girls when they reach puberty. If you want to learn more about sexual maturity and fertility development, we recommend continuing your reading here: Female Fertility – Parts of the Female Reproductive System.

Some fertility-related diseases are diagnosed in women when they reach puberty and do not have menstruation. By performing gynecological tests, the doctor may discover an absence of the uterus or some genetic alteration. These could be the cases of Rokitansky syndrome and Turner syndrome, respectively.

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FAQs from users: 'How do I distinguish implantaton bleeding from my period?', 'What is period for?', 'Is menstrual pain related to fertility?', 'Can menstruation be affected by tubal ligation?', 'How can menstruation be distinguished from implantation bleeding?' and 'What if the period is scanty and short on time?'.

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Authors and contributors

 Elena Izquierdo Trechera
Elena Izquierdo Trechera
M.D., M.Sc.
Bachelor's Degree in Medicine by the Complutense University of Madrid. Specialist in Obstetrics & Gynecology. Master's Degree in Human Reproduction by the King Juan Carlos University and the IVI. Currently, she is currently a gynaecologist specialising in assisted reproduction at the Eugin clinic in Madrid. More information about Elena Izquierdo Trechera
License: 282866949
 Guillermo Quea Campos
Guillermo Quea Campos
Guillermo Quea, MD has a degree in Medicine and Surgery from the University of San Martin de Porres. He also has a Master's Degree in Human Reproduction from the Universidad Rey Juan Carlos and another in Public Health and Preventive Medicine from the Universidad del País Vasco. More information about Guillermo Quea Campos
Member number: 282860962
 Marta Barranquero Gómez
Marta Barranquero Gómez
B.Sc., M.Sc.
Graduated in Biochemistry and Biomedical Sciences by the University of Valencia (UV) and specialized in Assisted Reproduction by the University of Alcalá de Henares (UAH) in collaboration with Ginefiv and in Clinical Genetics by the University of Alcalá de Henares (UAH). More information about Marta Barranquero Gómez
License: 3316-CV
 Zaira Salvador
Zaira Salvador
B.Sc., M.Sc.
Bachelor's Degree in Biotechnology from the Technical University of Valencia (UPV). Biotechnology Degree from the National University of Ireland en Galway (NUIG) and embryologist specializing in Assisted Reproduction, with a Master's Degree in Biotechnology of Human Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI) More information about Zaira Salvador
License: 3185-CV
Adapted into english by:
 Michelle Lorraine Embleton
Michelle Lorraine Embleton
B.Sc. Ph.D.
PhD in Biochemistry, University of Bristol, UK, specialising in DNA : protein intereactions. BSc honours degree in Molecular Biology, Univerisity of Bristol. Translation and editing of scientific and medical literature.
More information about Michelle Lorraine Embleton

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