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Normal Menstrual Cycle

Overview

The menstrual cycle is the series of changes the body goes through to prepare for a possible pregnancy. About once a month, the lining of the uterus (endometrium) starts to thicken. Then an ovary releases an egg. If the egg is fertilized by sperm and attaches to the lining of the uterus (implants), pregnancy begins. If the egg isn't fertilized or a fertilized egg doesn't implant, the uterus sheds its lining. This is the monthly menstrual bleeding, or period. Periods happen from the early teen years until menopause, around age 50.

A normal cycle lasts from 21 to 35 days. Count from the first day of one menstrual period until the first day of your next period to find the number of days in your cycle.

You may have no discomfort during your menstrual cycles. Or you may have mild to severe symptoms. If you have problems, ask your doctor about over-the-counter medicine. It may help relieve pain and bleeding.

What controls your menstrual cycle?

Your hormones control your menstrual cycle. During each cycle, your brain's hypothalamus and pituitary gland send hormone signals back and forth with your ovaries. These signals get the ovaries and uterus ready for a pregnancy.

The hormones estrogen and progesterone play the biggest roles in how the uterus changes during each cycle.

  • Estrogen builds up the lining of the uterus.
  • Progesterone increases after an ovary releases an egg (ovulation) at the middle of the cycle. This helps keep the lining ready for a fertilized egg.
  • A drop in progesterone (along with estrogen) causes the lining to break down. This is when your period starts.

A change in hormone levels can affect your cycle. Other things can also change your cycle. They include birth control pills, low body fat, losing a lot of weight, being overweight, stress, and very hard exercise training. Pregnancy is the most common cause of a missed period.

What symptoms are linked to the menstrual cycle?

For about a week before a period, some people may have premenstrual symptoms. You may feel irritable. You may gain water weight and feel bloated. Your breasts may feel tender. You may get acne. You also may have less energy than usual. A day or two before your period, you may start to have pain (cramps) in your belly, back, or legs. Cramps can range from mild to severe. These symptoms go away during the first days of a period. And some people have no symptoms.

When your ovary releases an egg in the middle of your cycle, you may have pain in your lower belly. You also might have red spotting for less than a day. Both are normal.

How can you manage menstrual bleeding?

You can choose from a range of pads, tampons, or menstrual cups to manage menstrual bleeding. Follow all directions included with the product of your choice. You may have to try different products to find out what's right for you. Whichever you use, be sure to change it regularly. This helps prevent leakage and infection.

How can you manage menstrual cycle symptoms?

Getting regular exercise, eating a variety of healthy foods, and reducing stress may help menstrual symptoms. It may also help to limit food and drinks that make your symptoms worse, such as alcohol or caffeine.

Ask your doctor if you can take an over-the-counter medicine to help relieve your menstrual symptoms. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil), can reduce menstrual cramps, pain, and bleeding by lowering the level of the hormone prostaglandin. If NSAIDs don't relieve the pain, try acetaminophen (Tylenol). Take the medicine for as long as the symptoms would normally last.

You can also try other ways to relieve menstrual cramps:

  • Apply a heating pad set on low or hot water bottle to your belly. Or take a warm bath.
  • Lie down, and prop up your legs by putting a pillow under your knees.
  • Lie on your side, and bring your knees up toward your chest.
  • Exercise.

Normal Menstrual Cycle

The menstrual cycle is the series of changes in the body to prepare for a pregnancy. About once a month, the lining of the uterus (endometrium) starts to thicken. Then an ovary releases an egg. If the egg is fertilized by sperm and attaches to the lining of the uterus (implants), pregnancy begins. If the egg is not fertilized or a fertilized egg does not implant, the lining of the uterus is shed. This is the monthly menstrual bleeding (also called menstruation or menstrual period) that happens from the early teen years until menopause, around age 50.

The menstrual cycle is from Day 1 of bleeding to Day 1 of the next time of bleeding. The average cycle is 28 days. But it's normal to have a cycle that is shorter or longer. For example:

  • A teen's cycles may be long (up to 45 days), growing shorter over several years.
  • Between ages 25 and 35, cycles are often regular. They generally last 21 to 35 days.
  • Around ages 40 to 42, cycles tend to be the shortest and most regular. This is followed by 8 to 10 years of longer, less predictable cycles until menopause.

Menstrual periods usually start around age 12. But it may start earlier or later. It's common to have fewer periods between ages 39 and 51. If you are in your teens or in your 40s, you may have cycles that are longer or that change a lot. If you are a teen, your cycles should even out with time. If you are nearing menopause, your cycles will probably get longer and then will stop.

Phases of the menstrual cycle

The three phases of your menstrual cycle are triggered by hormonal changes.

Menstrual period

On day 1 of your cycle, the thickened lining (endometrium) of the uterus starts to shed. You know this as menstrual bleeding from the vagina. A menstrual period can last about 4 to 6 days.

Most of your menstrual blood loss happens during the first 3 days. This is also when you might have cramping pain in your pelvis, legs, and back. Cramps can range from mild to severe. The cramping is your uterus contracting, helping the endometrium shed. In most cases, any premenstrual symptoms that you've felt before your period will go away during these first days of your cycle.

Follicular phase

During the follicular phase, an egg follicle on an ovary gets ready to release an egg (ovulation). Usually, one egg is released each cycle. This process can be short or long. It plays the biggest role in how long your cycle is. At the same time, the endometrium starts to thicken to get ready for a fertilized egg.

The last 5 days of the follicular phase, plus ovulation day, are your fertile window. This is when you are most likely to become pregnant if you have sex without using birth control.

Luteal (premenstrual) phase

This phase starts on ovulation day, the day the egg is released from the egg follicle on the ovary. It can happen anytime from day 7 to day 22 of a normal menstrual cycle. During ovulation, you may have less than a day of red spotting or lower pelvic pain or discomfort (mittelschmerz). These signs of ovulation are normal.

  • If the egg is fertilized by sperm and then implants in (attaches to) the endometrium, a pregnancy begins. (This pregnancy is dated from day 1 of this menstrual cycle.)
  • If the egg isn't fertilized or a fertilized egg doesn't implant, the endometrium starts to break down.

After the teen years and before perimenopause in your 40s, your luteal phase is very predictable. It normally lasts 13 to 15 days, from ovulation until menstrual bleeding starts a new cycle. This 2-week period is also called the "premenstrual" period.

It's common to have premenstrual symptoms during all or part of the luteal phase. You may feel irritable. You may gain water weight and feel bloated. Or you may have acne or tender breasts. A day or more before your period, you may start to have pain (cramps) in your belly, back, or legs. It's normal to have less energy at this time. You may also have headaches, diarrhea or constipation, nausea, or dizziness. When premenstrual symptoms make your daily life difficult, you are said to have premenstrual syndrome (PMS).

Menarche and the Teenage Menstrual Cycle

Menarche (say "MEN-ar-kee") is your first menstrual period. Your period is a part of your menstrual cycle. This is a series of changes your body goes through to prepare for a possible pregnancy.

Perimenopausal Menstrual Cycle

Perimenopause is the process of change that leads up to menopause. It can start as early as your late 30s or as late as your early 50s. How long perimenopause lasts varies, but it usually lasts from 2 to 8 years. You may have irregular periods or other symptoms during this time.

Managing Menstrual Cycle Symptoms and Bleeding

Getting regular exercise, eating a variety of healthy foods, and reducing stress may help menstrual symptoms. It may also help to limit food and drinks that make your symptoms worse, such as alcohol or caffeine.

Keep track of the day you start your menstrual period each month. If your cycle is regular, the calendar can help you predict when you'll have your next period.

To help you figure out if you have a pattern of premenstrual symptoms, try keeping track of your symptoms.

Medicine for menstrual pain and bleeding

Ask your doctor if you can take an over-the-counter medicine to help relieve your menstrual pain and bleeding. Start to take the recommended dose of pain reliever when symptoms start or 1 day before your period starts. If you are trying to become pregnant, talk to your doctor before you use any medicine.

  • Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (for example, Advil), reduce menstrual cramps, pain, and bleeding by lowering the level of the hormone prostaglandin.
  • If NSAIDs don't relieve the pain, try acetaminophen, such as Tylenol.
  • Take the medicine for as long as the symptoms would normally last if you didn't take the medicine.

Other ways to relieve menstrual cramps

Here are more ways to relieve menstrual cramps:

  • Apply heat to your belly with a heating pad or hot water bottle. Or take a warm bath. Heat improves blood flow and may decrease pelvic pain.
  • Lie down and prop up your legs by putting a pillow under your knees.
  • Lie on your side, and bring your knees up toward your chest. This will help relieve back pressure.
  • Exercise. This improves blood flow, produces pain-fighting endorphins, and may reduce pain.

How to manage menstrual bleeding

You can choose from a range of pads, tampons, or menstrual cups to manage menstrual bleeding. Follow all directions included with the product of your choice.

  • Pads range from thin and light to thick and superabsorbent. They protect your clothing.
  • Tampons range from small to large, for light to heavy flow. You can place a tampon in your vagina by using a slender tube (packaged with the tampon) or by placing it with a finger. Tampons should be changed at least every 4 to 8 hours.
  • Menstrual cups are inserted in the vagina to collect menstrual flow. You remove the menstrual cup to empty it. Some are disposable. Others can be washed and reused. Menstrual cups can be worn for up to 12 hours.

You may have to try different products to find out what is right for you. Whichever you use, be sure to change it regularly. This helps prevent leakage and infection.

When to Call a Doctor

Any change in your menstrual pattern or amount of bleeding that affects your daily life should be checked by a doctor. This can include:

  • Getting your period more or less often than normal. A normal adult menstrual cycle is about 21 to 35 days long. A normal teen cycle is about 21 to 45 days.
  • Periods that last longer than 7 days.
  • Periods that are lighter or heavier than usual. With heavy bleeding, you may soak through your pads or tampons often.
  • Not getting your period for more than 3 months.
  • Bleeding when you don't expect to, such as between periods or after sex.
  • Pelvic pain that is not linked to menstrual bleeding and lasts longer than a day.

If you are a teenager, see your doctor if you have not started having periods by age 15.

Credits

Current as of: November 22, 2021

Author: Healthwise Staff
Medical Review:
Sarah Marshall MD - Family Medicine
Martin J. Gabica MD - Family Medicine
Kathleen Romito MD - Family Medicine