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The Menstrual Phase of Menstruation: Understanding the Basics

Updated: Jun 25

Woman experiencing period cramps

For many of us, when we say our menstrual cycle, it is what we commonly refer to as "having our period" and we absolutely dread it. However, despite our negative feelings about it, our menstrual cycle is a vital aspect of reproductive health. So let's clear up some common misconceptions and cover the basics of what exactly it means to "be on your period."

The first thing you should know is that the menstrual cycle is not just the days that you bleed, but it actually starts on the first day of your period and ends the day before the next period. Some of us have shorter cycles and some of us have longer ones.

The average cycle is considered to be 28 days, however, anything between 21 and 35 days is considered normal. Bleeding usually lasts for 3-7 days. For the first year or two after menstruation begins, there is a tendency to have longer cycles and they do not always start at the same time every month. The menstrual cycle on average starts at the age of 12. However, you can begin menstruating as early as 8 years old or as late as 16 years old. As you get older, you may find like many other women, that you may start having shorter, more consistent cycles. Women stop menstruating at menopause, which typically occurs at about the age of 51.

So to be clear, the menstrual cycle encompasses several phases that prepare the female body for a potential pregnancy. That being said, as we go along this series, you will begin to see that even if pregnancy is not in your plans, maintaining a healthy menstrual cycle is still critical for your overall health.

What is the Menstrual Phase?

The first and the most recognizable phase of the menstrual cycle is the menstrual phase, commonly referred to simply as menstruation. This phase marks the beginning of the menstrual cycle. During this phase, the body expels the thickened lining of the uterus (endometrium), which was prepared in the previous cycle in anticipation of a possible pregnancy. This shedding process results in menstrual bleeding, commonly known as a period. Understanding the menstrual phase is crucial for recognizing normal bodily functions and identifying any potential health issues. This article specifically delves into the details of the menstrual phase, its significance, and how to manage it effectively.

The Biological Process

Hormonal Changes: At the start of the menstrual phase, the levels of estrogen and progesterone drop significantly. These hormones, produced by the ovaries, play a crucial role in regulating the menstrual cycle. As a matter of fact, at this phase of the menstrual cycle, these hormones are typically at their lowest. The decrease in these hormone levels signals the body that pregnancy has not occurred, prompting the shedding of the uterine lining.

Shedding of the Endometrium: The endometrium is a mucous membrane lining the inside of the uterus. It thickens each cycle to provide a nourishing environment for a potential embryo. When fertilization does not occur, this lining is no longer needed and is shed through the vagina as menstrual blood, which includes blood, mucus, and tissue. Menstruation is necessary to prevent build-up of the endometrium. The shedding of the womb lining allows growth of new endometrium for the next menstrual cycle.

Menstrual Flow: Menstrual flow can vary in volume and consistency. On average, individuals lose about 30 to 80 milliliters of blood during their period. Menstrual blood can appear bright red, dark brown, or even black, depending on how long it has been in the uterus. Pink blood is often seen at the time your period starts. As your uterus starts to actively shed blood during your period, you may notice that the color changes to a bright red. This means that your blood is fresh and has not been in the uterus for a long time. Dark red, brown or black blood is normal and is simply blood that has been in the uterus for longer. This is because, the longer it stays inside your uterus, it starts to react with oxygen. This reaction is what causes the color to get darker. The longer the blood stays inside your body, the darker it gets. Sometimes, as your period comes to an end, the dark blood can mix with vaginal discharge and end up looking brown. Your menstrual flow can be sometimes be accompanied by blood clots. Clotting is considered normal unless the clots are larger than the size of quarters, in which case you will need to see a health care provider. 

Symptoms and Management during The Menstrual Phase

The menstrual phase can come with a variety of physical, emotional, and behavioral symptoms. These symptoms typically start in the 5 days before menstruation begins and stop within 4 days after bleeding starts. Some of the most common Premenstrual Symptoms (PMS) include:

  • Menstrual Cramps: These are caused by the contraction of the uterus to help expel its lining. Over-the-counter pain relievers can help alleviate cramps.

  • Bloating and Water Retention: Hormonal changes can cause the body to retain water, leading to bloating. Staying hydrated and reducing salt intake can help manage these symptoms.

  • Mood Changes: Fluctuations in hormone levels can affect mood for example, depression, feeling stressed, angry, upset, anxious or irritable. Engaging in relaxation techniques, such as yoga or meditation, can be beneficial.

  • Appetite Changes and Food Cravings: Some women find themselves binge eating, others find they have no appetite.

  • Breast Tenderness: Hormonal shifts can lead to swollen or tender breasts. Wearing a supportive bra can provide relief.

  • Low Energy Levels: Hormonal shifts can lead to tiredness or trouble falling and/or staying asleep (insomnia) or over sleeping.

  • Change in Bowel Movements: Some women experience constipation or diarrhoea.

  • Pain and Discomfort: Some women experience headaches/migraines, back pain as well as other joint or muscle pains.

  • Poor Concentration: Many women struggle to concentrate and complain of feelings of brain fog and forgetfulness.

  • Other Common Symptoms: Acne flare-ups, greasy hair, low tolerance for noise or light, body temperature changes (feeling too hot or too cold).

Menstrual Hygiene

Maintaining good menstrual hygiene is essential for comfort and health during the menstrual phase. Various menstrual products are available to manage menstrual flow:

  • Sanitary Napkins (Pads): These are absorbent pads that adhere to the underwear and collect menstrual blood externally. Pads should be changed every 3–4 hours, even if you have a light flow. Regular changing prevents buildup of bacteria and odor. If you have a heavier flow then you may need to change pads more often to make sure you don't leak.

  • Tampons: Inserted into the vagina, tampons absorb menstrual blood internally. Some tampons come with an applicator made from either plastic or cardboard that guides the tampon into the vagina. Other tampons are inserted using a finger. It is very important to change tampons every few hours and that you wear the absorbency type that is right for you. Change a tampon every 4–6 hours or when it's saturated with blood.

  • Menstrual Cups: These are reusable cups made of silicone or rubber that collect menstrual blood inside the vagina. You can't see when the cup is full, so you will need to empty it several times a day. Be sure to follow the instructions that accompanies the cup.

  • Menstrual Discs: Flat, flexible discs inserted into the vagina, positioned at the cervix to collect menstrual blood. Like the menstrual cup, it can stay in for up to 12 hours. Discs can be disposable or reusable. Reusable discs are made from medical-grade silicone and can be reused for several years.

  • Period Panties: These are specially designed underwear that can absorb menstrual blood and be worn alone or as backup protection.

  • Panty Liners: Smaller and thinner pads used for light menstrual flow or as a backup with other products, such as tampons.

  • Reusable Cloth Pads: Washable fabric pads that attach to underwear with snaps or Velcro.

Considerations for Choosing Menstrual Products

  • Flow Intensity: Choose based on the amount of menstrual flow.

  • Comfort: Personal comfort and lifestyle preferences (e.g., active lifestyle, sensitivity).

  • Environmental Impact: Reusable products are more environmentally friendly than disposables.

  • Cost: Initial investment and long-term cost.

  • Convenience: Ease of use, cleaning, and maintenance.

Each person’s needs and preferences can vary, so it may take some experimentation to find the best combination of products.

When to Seek Medical Advice

While the menstrual phase is a normal part of the menstrual cycle, it is important to seek medical advice if you experience any unusual or concerning symptoms related to your menstrual cycle. Here are specific instances when you should consider consulting a healthcare provider:

  • Heavy Bleeding: If you need to change your pad or tampon every hour or have large blood clots, you may have menorrhagia (heavy menstrual bleeding).

  • Severe Menstrual Cramps (Dysmenorrhea): If menstrual cramps are severe enough to interfere with daily activities and do not improve with over-the-counter pain relievers. Intense menstrual cramps that do not respond to over-the-counter pain relief could indicate conditions like endometriosis or fibroids.

  • Pelvic Pain: Persistent or severe pelvic pain that occurs at any time in the menstrual cycle, not just during menstruation.

  • Irregular Periods: If your periods are consistently irregular (e.g. occurring more or less frequently than the usual 21-35 day cycle) or if there are sudden changes in your menstrual cycle pattern.

  • Missed Periods: If you miss periods frequently and are not pregnant. If you suddenly stop having periods (amenorrhea) for three or more months without an obvious cause (such as pregnancy, menopause, or certain contraceptives).

  • Heavy Menstrual Bleeding (Menorrhagia): If you need to change your tampon or pad every hour for several consecutive hours. If your period lasts more than seven days and/or if you are passing large blood clots (larger than a quarter).

  • Bleeding Between Periods: If you experience spotting or bleeding between periods. Any postmenopausal bleeding.

  • Unusual Discharge: If you notice any unusual vaginal discharge with a strong odor, unusual color, or accompanied by itching or irritation.

  • Significant Mood Changes: Severe mood swings, depression, or anxiety that are linked to your menstrual cycle.

  • Unexpected Weight Changes: Unexplained weight loss or gain associated with menstrual irregularities.

  • Signs of Anemia: Feeling unusually tired, shortness of breath, or having pale skin, which could indicate anemia due to heavy menstrual bleeding.

  • Symptoms of Infection: Fever, chills, and severe abdominal pain. While some menstrual irregularities and discomforts can be normal, persistent, severe, or unusual symptoms should be evaluated by a healthcare provider. Early diagnosis and treatment can help manage any underlying conditions and improve your quality of life.


The menstrual phase is a fundamental part of the menstrual cycle, marking the beginning of a new cycle with the shedding of the uterine lining. Understanding this phase, its symptoms, and how to manage them can help individuals maintain their menstrual health and well-being. By paying attention to changes and seeking medical advice when necessary, individuals can ensure they are managing their menstrual health effectively.

This article is part of a series on the menstrual cycle and menstrual health.

For part one, click here.

For part three, click here.

This article is for informational purposes only and is not meant to offer medical advice.

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