If a person taking a birth control pill misses a period, they may wonder if they are pregnant. However, a range of other factors may be responsible.

Birth control pills are a popular and practical method of contraception. There are several types, and each contains different combinations of hormones that can affect the menstrual cycle.

The term for the absence of an expected period is amenorrhea. Experiencing this while taking a birth control pill is common.

In this article, learn what factors can cause a person to miss a period while on a birth control pill.

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Birth control pills can prevent ovulation and should be effective in 99 percent of cases.

Birth control pills contain different hormones that prevent pregnancy. The hormones can:

  • prevent ovulation
  • thin the uterine lining, preventing fertilized eggs from implanting
  • cause the cervical mucus to thicken, preventing sperm from reaching the egg

Birth control pills are usually organized by week, with the pills of the first three weeks containing hormones, and the pills of the final week containing no active medication. These placebos simply help a person to remember to take a pill each day.

When taken correctly, birth control pills are collectively estimated to be effective in around 99 percent of cases.

However, people tend to skip doses. Also, if a person is vomiting, they may not fully ingest the pill. These factors can reduce effectiveness, and may lead to an increased risk of pregnancy or irregular bleeding.

Any of the following factors can lead to a missed period while on birth control.

The type of pill

Some birth control pills can cause periods to stop or become irregular. Other types, sometimes called seasonal pills, can cause a person to have only four periods a year.

Everyone is different, and the effects of pills are not always predictable. If a person has recently started taking a new pill, the body may need time to adjust, and this can cause a missed period.

Stress

Stress can affect the menstrual cycle, causing it to extend or shorten. In some cases, stress can cause periods to stop altogether.

Rapid weight loss

Losing weight quickly can strain the body. For example, if a person is on an extreme diet, a lack of calories can prevent the production of hormones required for ovulation.

Being overweight or obese

Overweight women can produce an unusually high amount of estrogen. This can cause periods to become irregular or stop.

Overexercising

Intense exercise can put excessive strain on the body and may lead to a hormonal imbalance. This can cause irregular periods.

Illness

Some illnesses can cause periods to stop. The most common is polycystic ovary syndrome.

If periods stop, and pregnancy is not the cause, a doctor may perform additional tests, to rule out certain medical conditions.

Pregnancy

While pills can be a very reliable method of contraception, they are not always effective. Though the chances are rare, a person can get pregnant while on a contraceptive pill.

Anyone who suspects that they are pregnant should take a test, to help eliminate uncertainty.

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When taking a birth control pill, it is still possible for a person to become pregnant.

Pregnancy is just one of many reasons that a person can miss a period.

It is important to be aware that a person can become pregnant, even when taking a birth control pill as instructed. Anyone who is sexually active and has missed a period, or had only light spotting, should take a pregnancy test or make an appointment with a doctor.

Chances of becoming pregnant increase when a person skips a pill. The majority of these pregnancies occur when a person has missed two or more doses in a row.

Other early signs of pregnancy include:

  • nausea or vomiting
  • breast tenderness
  • low energy levels and sluggishness
  • aching in the lower back
  • urinating more frequently than usual

Some of these signs can appear as soon as 1 week after a missed period. If a person has not had an expected period and experiences any of the other symptoms of pregnancy, they should take a test.

The birth control pill birth regulates the menstrual cycle. Most types of pill work in 4-week cycles. A person on one of these pills can expect a period about every 28 days.

Depending on the type of birth control, some people may experience periods more frequently than usual. For others, periods may stop.

The easiest way to determine the cause of a missed period is to take a pregnancy test. A person can buy one to take at home or make an appointment with a doctor.

Missed periods can signal underlying medical conditions. If periods continue to be irregular or stop unexpectedly, make an appointment with a doctor.

The doctor may ask about a person's medical history, their sexual history, and their family's medical history, among other questions.

If the doctor suspects an underlying condition, they may perform further testing or refer the person to a specialist.