Think of the menstrual cycle as a hormone-driven 30-day calendar your body follows naturally. Day one is when you begin your period and start to bleed, called menstruation. This bleeding typically ends on day three or five. On day 14, ovulation will occur. If the egg is not fertilized by the 25th day, it will dissolve, hormone levels will stabilize and the cycle will start over again. But what to do about a sudden change in menstrual cycle length?

Everyone’s menstrual cycle is a little different. Many people experience irregular periods, menstruation that is less frequent or lasts longer than average. If you’ve noticed changes in your menstrual cycle length, you’re not alone — 14% of women experience irregular periods.

There are many causes for a sudden change in menstrual cycle length, including the five below.

You Could Be Pregnant

If you’ve noticed a change or missed your period altogether, one common cause could be pregnancy. Your body generates a hormone called hCG (human chorionic gonadotrophin) when pregnant, which stops your period. Before six weeks, the placenta is still developing, during which you can experience light bleeding or spotting.

Take a pregnancy test if you’ve missed your period or it is lighter than usual. If positive, be sure to contact your doctor or gynecologist right away to schedule a wellness exam. While spotting is normal during pregnancy, it can also be the first sign of miscarriage.

You Could Be on Birth Control

Your sudden change in menstrual cycle length could be due to birth control. Even if you were already on birth control, switching to a new method can alter your hormone levels and cause changes to your period. The most common types of birth control that affect periods include pills, patches, IUDs (intrauterine devices) and vaginal rings.

Birth control pill packages typically include 21 days of active pills, leaving seven placebo pills to allow menses. More modern options include active pills that last for up to a year. Injected and implanted birth control can also cause sudden changes to your menstrual cycle, with many women reporting no periods at all.

You Could Have Endometriosis

Endometriosis is a disorder where the uterine tissue begins to grow on other parts of the body. It can cause symptoms like painful periods, heavy bleeding and infertility. Though experts aren’t clear on what causes the tissue to spread, endometriosis is a common issue that affects one of every 10 women between 15 and 49.

There are several treatment options available for those with endometriosis, even women with no symptoms. Hormonal birth control limits the growth of endometrial tissue and keeps the menstrual cycle on track. Over-the-counter pain relievers, like Motrin or Tylenol, can offer relief from pain.

You Could Have Uterine Fibroids

Uterine fibroids are tumors that grow on the uterine wall. Most of these fibroids are benign, though they can cause some pain.

There are four types of uterine fibroids, submucosal, intramural, subserosal and pedunculated.

• Intramural fibroids grow within the uterine wall.
• Subserosal fibroids grow outside the uterine wall.
• Submucosal fibroids thrive just below the surface of the uterus.
• Pedunculated fibroids dangle from stems inside and outside the uterus.

Intramural fibroids, the most common type of tumor, grow slowly and can be detected early. Submucosal fibroids, which can protrude through the uterine cavity, are rare but can be treated with minimally invasive surgery.

You Could Be in Perimenopause

Perimenopause is the time leading up to menopause, when your periods stop. This phase is different for all women and can last up to 10 years. Similar to puberty, perimenopause can affect hormone levels and alter ovulation, causing changes to your menstrual cycle. You could experience irregular bleeding or spotting. Some months, your period might be shorter and lighter. The number of days between your periods could increase, and you may even skip periods altogether.

This phase can be a confusing time, and it can be hard to determine what’s normal. If you experience heavy bleeding or bleeding more often than every three weeks, contact your doctor. Abnormal bleeding could be a sign of an underlying issue, such as polyps on the inside of the uterus.

Is a Sudden Change in Menstrual Length Worrisome?

There are plenty of reasons you may have noticed a sudden change in menstrual cycle length. From a new birth control method to perimenopause, your body is continually in a state of flux, trying to find the ideal balance of hormones.

You can try to regulate your periods naturally. If you don’t want to turn to medicine but still want the convenience of a regular and reliable period, try methods like regular exercise and a healthy diet. You can also take daily vitamins, which play a vital role in balancing and producing hormones.

If nothing works and you’re concerned about your changing menstrual cycle, schedule an appointment with your gynecologist. An expert will be able to address your concerns and help identify a solution.