What is a period?

A period, also called menstruation, is when your body removes the buildup of the lining of your uterus. This buildup of menstrual blood and tissue flows out of your vagina. The day your period starts is the first day of your menstrual cycle, which lasts until the first day of your next period.
Recognizing the signs that your period is coming helps you prepare to deal with the symptoms your body goes through during your menstrual cycle.
Signs of a period
You will probably feel certain symptoms in the days leading up to your period, including:
Tender breasts
Changes in hormone levels before menstruation can cause pain, swelling, and tenderness in your breasts before your period.
Headaches
When estrogen levels drop before your period, it can trigger headaches, including migraines.
Abdominal cramps
Menstrual cramps are throbbing, cramping pains caused by excessive chemicals produced by your uterus before your period that make the muscles in your uterus tighten and relax.
Muscle aches
You may also feel pain in your muscles, resulting in body aches.
Lower back pain
The pain caused by your abdominal cramps can also extend into your lower back, giving you lower back pain in the days leading up to your period.
Fatigue
Hormone changes before your period can affect your brain chemistry, making you feel more tired before menstruation. This can also cause sleep problems, which can contribute to your fatigue.
Bloating
Changes in your hormones can cause you to retain water before your period, making you experience bloating.
Joint pain
Estrogen is a hormone that helps control joint pain, but right before your period, your estrogen levels go down. This can increase your joint pain.
Acne
Changes in hormone levels can make your body produce more oil, which clogs your pores. This can cause you to develop pimples before your period begins.
Diarrhea or constipation
Your digestive system can experience changes when your period is coming, causing you to have diarrhea or constipation.
Premenstrual syndrome (PMS)
Premenstrual syndrome, or PMS, includes the range of emotional and physical symptoms you may experience in the days leading up to your period. In addition to the physical symptoms listed above, you may also experience mood-related symptoms. These can include:
- Irritability
- Trouble focusing
- Anxiety
- Sadness
- Anger
- Lack of interest in talking to others
- Crying spells

Causes of periods
During your menstrual cycle, one of your ovaries releases an egg. At the same time, the lining of your uterus builds up to prepare for a possible pregnancy. But if you don’t get pregnant, your estrogen and progesterone hormone levels fall and tell your body to start your period, flushing the buildup of menstrual blood and tissue through your vagina. Bleeding can last 2 to 7 days.
While most menstrual cycles are 28 days long, women experience different cycle lengths. Your menstrual cycle can also be altered by different factors, including:
- Birth control pills
- Pregnancy
- Breastfeeding
- Disordered eating
- Extreme weight loss
- Excessive exercise
You may get your first period between the ages of 8 and 15 and have a menstrual cycle longer than 38 days. As you get older, your menstrual cycles usually become more regular, but they may become irregular in your 40s. Once you experience menopause, your menstrual cycles end.

QUESTION
What is pelvic inflammatory disease (PID)? See AnswerWhen to see the doctor for your period
If your period lasts more than 7 days, if you experience strong pain, or if you have a heavy menstrual flow and need to change pads or tampons every hour, discuss your symptoms with your doctor.
You should also call your doctor if:
- You haven’t experienced a period in 90 days
- You have periods more often than once every 21 days
- You have periods less often than once every 35 days
Missed or irregular periods can be a sign of stress or a medical condition. Talk with your doctor to find the cause of your irregular periods and how to treat it.
Tests for periods
If you have abnormally heavy menstrual bleeding, your doctor may conduct a pelvic exam, rectal-vaginal exam, pelvic ultrasound, or other tests to learn the cause of your excessive bleeding. If you miss your period, a home pregnancy test will let you know if you’re pregnant. However, if it comes back negative, a doctor can conduct a blood test to determine if you’re pregnant or not.
Treatments for periods
Eating a healthy diet low in caffeine, alcohol, and salt helps manage premenstrual symptoms. Exercising, getting enough sleep, and reducing stress also help alleviate symptoms. However, if a healthy lifestyle and over-the-counter medication are not enough, a doctor can prescribe birth control pills and other medications to relieve your symptoms.
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AllinaHealth: "Is this normal? Your period in your 20s, 30s and 40s."
American College of Obstetricians and Gynecologists: "Dysmenorrhea: Painful Periods."
American College of Obstetricians and Gynecologists: "The Menopause Years."
BMC Women's Health: "Gastrointestinal symptoms before and during menses in healthy women."
Center for Young Women's Health: "Birth Control Pills: A Guide for Parents."
Journal of the American Academy of Dermatology: "The effect of the menstrual cycle on acne."
Journal of Exercise Rehabilitation: "Relation of the factor to menstrual pain and musculoskeletal pain."
Journal of Sleep Medicine and Disorders: "Sleep and Premenstrual Syndrome."
MedlinePlus: "Breast pain."
MedlinePlus: "Period Pain."
National Headache Foundation: "Menstrual Migraines."
Obstetrics and Gynecology International: "Fluid Retention over the Menstrual Cycle: 1-Year Data from the Prospective Ovulation Cohort."
Office on Women's Health: "What happens during the typical 28-day menstrual cycle?"
Penn Medicine: "Irregular Periods: Why is My Period Late?"
Texas Health Resources: "Period Protocol: When Is It Time to Call Your Doctor?"
The Journal of the American Medical Association: "The Length and Variability of the Human Menstrual Cycle."
The Society of Obstetricians and Gynaecologists of Canada: "Exams and Tests Used to Investigate Menstrual Disorders."
The Society of Obstetricians and Gynaecologists of Canada: "Premenstrual Syndrome (PMS)."
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