Menstruation
Regular discharge of uterine lining triggered by hormonal changes.
Menstruation, also known as a period, is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. It is triggered by falling progesterone levels and is a sign that pregnancy has not occurred. The menstrual cycle is characterized by the rise and fall of hormones, and feminine hygiene products are used to maintain hygiene during menses.
- First period (menarche)
- Usually between ages 11 and 13; as young as eight considered normal
- Typical cycle length (young women)
- 21 to 45 days
- Typical cycle length (adults)
- 21 to 35 days; average often cited as 28 days; mean from app data 29.3 days
- Bleeding duration
- Two to seven days
- Menopause age
- Usually between 45 and 55 years
- Average menstrual fluid volume
- 35 ml (1.2 US fl oz); typical range 10–80 ml
Lore & Background
The first period, menarche, usually begins during puberty between ages 11 and 13, though starting as young as eight is still considered normal. The average age of first period is later in the developing world and earlier in the developed world. The typical length between periods is 21 to 45 days in young women and 21 to 35 days in adults, with the average often cited as 28 days; the largest study of menstrual app data found a mean cycle length of 29.3 days. Bleeding typically lasts two to seven days. Periods stop during pregnancy and typically do not resume during initial months of breastfeeding; lochia occurs after childbirth. Menstruation ceases after menopause, which usually occurs between 45 and 55 years of age.
Reader's Guide
Menstruation is a key biological process marking reproductive potential and overall health. During their period, 38% of women reported being unable to perform all regular daily activities. Symptoms such as premenstrual syndrome (PMS) affect 20 to 30% of women, with 3 to 8% experiencing severe symptoms including acne, tender breasts, bloating, fatigue, irritability, and mood changes. Painful periods (dysmenorrhea) affect an estimated 50 to 90% of women, and heavy bleeding can lead to anemia. The menstrual cycle also interacts with other conditions: drops in estrogen may trigger migraines, and some women with epilepsy experience catamenial seizures linked to the cycle. Research indicates a higher likelihood of anterior cruciate ligament injuries in the pre-ovulatory stage. Understanding menstruation is essential for managing reproductive health, diagnosing disorders such as amenorrhea, and addressing the significant impact on daily life for many women.
Did You Know?
- The average menstrual cycle length from the largest app study is 29.3 days.
- About half of menstrual fluid is blood, containing sodium, calcium, phosphate, iron, and chloride.
- An enzyme called plasmin in the endometrium inhibits blood from clotting during menstruation.
- Some 20 to 30% of women experience premenstrual syndrome (PMS), with 3 to 8% having severe symptoms.
Frequently Asked Questions
What is Menstruation?
Menstruation, commonly called a period, is the regular shedding of blood and mucosal tissue from the uterine lining through the vagina. It signals that no pregnancy has occurred during that cycle.
What triggers Menstruation?
A drop in progesterone levels prompts the uterine lining to break down and be expelled. This hormonal shift is part of the broader cycle of rising and falling reproductive hormones.
How long does a typical Menstruation last?
Bleeding generally spans two to seven days. The full cycle from one period to the next usually runs 21 to 35 days in adults, with 28 days often cited as the average.
When does Menstruation first appear and when does it stop?
Menarche, the first period, typically arrives between ages 11 and 13, though onset as early as eight is still within the normal range. Menopause, the permanent end of cycles, most often occurs between 45 and 55 years of age.
How much fluid is lost during Menstruation?
The average volume of menstrual fluid is about 35 ml (roughly 1.2 US fluid ounces), with a normal range spanning 10 to 80 ml. Feminine hygiene products are used to manage this flow and maintain cleanliness.
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