What’s the menstrual cycle?
The menstrual cycle is the body’s monthly process to prepare for pregnancy. During the cycle, the lining of the uterus thickens. If you don't get pregnant, your hormone levels go down. This starts your period.1
The cycle starts on the first day of bleeding and ends at the start of the next period. It usually lasts about 28 days. Hormone changes can cause different symptoms. Every person’s cycle might be different, but the process is the same.1, 2
What are the 4 phases of the menstrual cycle?
Menses: Days 1–7
The menses cycle begins on the first day of your period. This is when the lining of the uterus sheds if pregnancy hasn’t occurred. This phase typically lasts 3 to 7 days.1, 2, 3
Follicular: Days 1–12
This phase starts on the first day of your period and ends at ovulation. Estrogen increases, and follicle-stimulating hormone (FSH) is released. This causes the follicles in your ovaries to grow. During days 10–14, one of the follicles will form a mature egg.2, 3
Ovulation: Days 12–14
During this stage, your body releases luteinizing hormone (LH). This hormone causes the ovary to release the mature egg. This is ovulation. High LH indicates window in your cycle when you're most likely to get pregnant.2, 3, 4
Luteal: Days 15–28
The last phase lasts about 2 weeks. The egg moves to the uterus as progesterone increases, thickening the uterine lining. If the egg is fertilized, pregnancy starts. If not, the lining sheds and your period begins. 2, 3
Menstrual cramps
The pain that you may have with your periods is called dysmenorrhea. This pain may feel like cramps, heaviness in the abdomen (belly) or tugging in the pelvic area.5 There are 2 types of dysmenorrhea:5
Primary dysmenorrhea
The most common type of period cramps. They are caused by contractions in the uterus to shed the lining. Cramps may start when you get your first period. The pain may lessen as you get older. You may be more likely to get severe cramps if you:
- Got your first period before age 11
- Have heavier or longer periods
- Have high levels of stress
- Smoke
Secondary dysmenorrhea
Usually caused by another health problem. The pain may get worse as you get older. Conditions that may cause secondary dysmenorrhea include:
- Endometriosis – when the lining of the uterus grows where it doesn’t belong
- Ovarian cysts – fluid-filled sacs in the ovary
- Uterine fibroids – tumors (almost always noncancerous) that grow in or on the wall of the uterus
Talk to your doctor if the pain affects your daily activities or if pain happens other than before or during your period. You should also talk to your doctor if you have blood clots larger than a quarter during your period.5
Premenstrual syndrome
Premenstrual syndrome (PMS) is the name for a combination of symptoms that start 1–2 weeks before your period. Most people get some PMS symptoms. They are most common in your 30s.6 For some, the symptoms are mild. Severe symptoms may be a sign of premenstrual dysphoric disorder (PMDD).6
Emotional PMS symptoms6
- Feeling grumpy or angry
- Tiredness and sleeping too much or too little
- Food cravings
- Hard to focus or remember things
- Feeling tense or worried
- Feeling sad or crying
- Mood changes
- Less interested in sex
Physical PMS symptoms6
- Sore or swollen breasts
- Constipation or diarrhea
- Feeling bloated or gassy
- Stomach cramps
- Headache or back pain
- Feeling clumsy
- Not liking loud sounds or bright lights
In the days leading up to your period, symptoms of other health problems may worsen, such as:7
- Anxiety and depression
- Asthma
- Diabetes (glucose levels may be harder to control)
- Irritable bowel syndrome (IBS)
- Migraine
What menstrual products should I use?
There are many types of period products available. Products that are scented may irritate your skin. Common period products include:8
- Sanitary pads – Also known as maxi pads, these disposable cotton pads stick to your underwear. Some have “wings” to help prevent leaks. Pads come in various sizes for different flows, and should be changed every 3–4 hours.8, 9
- Tampons – disposable cotton plugs inserted into the vagina, often with plastic applicators. Change every 4–6 hours to avoid toxic shock syndrome (TSS). Use the lowest absorbency needed.9
- Menstrual cups – Soft silicone or rubber cups inserted into the vagina to collect blood. They come in various sizes and can be disposable or reusable. Don’t leave one in for more than 12 hours.8, 10
- Period underwear – A type of underwear that absorbs menstrual blood and comes in various styles. It can be worn all day, sometimes with another product for extra protection. Wash like regular underwear.8
How long does a period normally last?
On average, most periods last between 2 and 7 days. The heaviest bleeding is typically in the first 3 days.11
Irregular menstrual cycles
The length of your period and the flow can vary from month to month. Irregular menstruation may look like:12
- Bleeding between periods, after menopause or after sexual intercourse
- Bleeding that is much heavier or lighter than usual
- Cycles that vary in length more than 9 days (For example, a cycle that is 25 days, then 35 days, then 24 days)
- Missing 3 or more periods in a row
- Periods that are fewer than 21 days or more than 35 days apart
- Periods that last longer than 7 days
- Severe pain, cramping, nausea or vomiting with your period
- Soaking through one or more tampons or sanitary pads in an hour
Irregular periods can happen for different reasons. These include endometriosis or polycystic ovary syndrome (PCOS). Talk to your doctor if you notice changes in your cycle or begin to have irregular cycles.12
Frequently asked questions about menstruation
The average amount of blood lost during a period is 2–3 tablespoons. Everyone is different, and you can lose more or less from month to month. Your period may also change as you get older. During perimenopause, some people have heavy bleeding.2
About 2 weeks before your period, an ovary releases an egg. This is ovulation. You are most likely to get pregnant if you have sex without birth control in the 3 days before or on the day of ovulation. During vaginal intercourse, the penis releases semen into the vagina. The semen has sperm, which can travel to the egg. If a sperm joins the egg (fertilization) pregnancy can happen.1 Learn more about the early signs of pregnancy.
Irregular or missed periods may be signs of an ovulation problem, the most common cause of female infertility. PCOS and primary ovarian insufficiency (POI) are common sources of ovulation problems.13 Unexplained infertility is when no cause is found.14 Learn more about family building and fertility treatments.
Everyone’s cycle is different. Ovulation usually happens about 5–7 days after your period ends. You do not ovulate when you are pregnant or after menopause. You might not ovulate while breastfeeding or during perimenopause. Ask your doctor about birth control if you do not want to get pregnant.1
Many people ease menstrual cramps with over-the-counter (OTC) pain medicine. Nonsteroidal anti-inflammatory drugs (NSAIDs) are common OTC medicines used to treat cramps. NSAIDs include naproxen, ibuprofen or aspirin.5, 15
Depending on the severity of your symptoms, your doctor may recommend hormonal birth control, such as the pill, the patch or the vaginal ring, to treat painful periods. A hormonal intrauterine device (IUD) can also be used to treat painful periods. An IUD may also lessen or stop menstrual bleeding.16
Other options that may help include aerobic exercise, taking a warm bath, applying heat to your abdomen, getting quality sleep and relaxing.16
Breastfeeding can delay the return of ovulation and menstruation after giving birth. However, it is not a form of birth control. If you do not want to get pregnant, talk to your doctor about birth control options that you can use while breastfeeding.17
It’s important to check in with your doctor about your reproductive health. You can do this during your yearly wellness visit with your primary care provider (PCP), obstetrician or gynecologist (OB/GYN). Talk to your provider if you:
- Bleed between periods
- Haven’t had a period for 3 months or longer
- Have lighter, heavier, longer or shorter periods than usual
- Think you may be pregnant
Some conditions may require immediate care. In a life-threatening situation, call 911 or go to your hospital emergency room (ER).
How do I find a provider to see about my period?
If you’re a member with UnitedHealthcare health insurance, use our provider search. This tool can help you find an OB/GYN or other health care provider who has special training in providing care for women.