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Common Causes of Breakthrough Bleeding and Spotting

Medically reviewed by Jobelle Ann Dela Cruz Bigalbal, MD · General Practitioner

Written by Lorraine Bunag, R.N. · Updated Jan 05, 2021

Common Causes of Breakthrough Bleeding and Spotting

Oral contraceptive pills contain the hormones estrogen and progestin, which prevent ovulation or the process where the ovaries release mature egg cells. Since a woman who takes birth control pills doesn’t ovulate, she does not experience menstruation. However, bleeding can sometimes happen even while on birth control pills. This is called breakthrough bleeding. In this article, we’ll talk about the most common causes of breakthrough bleeding.

Breakthrough bleeding, defined

Breakthrough bleeding happens when the woman experiences “unscheduled’ or unexpected bleeding while taking oral contraceptives. While it causes a certain level of concern, reports say that breakthrough bleeding is a common side effect of birth control pills. But why exactly does breakthrough bleeding happen?

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Common causes of breakthrough bleeding

If you experience breakthrough bleeding, it’s probably because:

You’ve just started taking birth control pills

Just starting your first pack of birth control pills is the most common cause of breakthrough bleeding. According to doctors, it takes some time for your body to get used to the hormonal changes, so bleeding might occur in the first 3 to 6 months. Moreover, breakthrough bleeding is also likely if you recently switched from one type of oral contraception to another or if your pills contain a low dose of estrogen. 

If you experience bleeding for longer than 6 months or suddenly have spotting while on an oral contraceptive that you’ve been using for a long time, make an appointment with your doctor.

You missed a dose

Another of the most common causes of breakthrough bleeding is skipping or missing a dose, or taking the pill late. To avoid breakthrough bleeding, it’s crucial to take the pills as scheduled, preferably at the exact same time each day (this is especially true for progestin-only pills).

You’re taking progestin-only pills

Some of the newer forms of oral contraception do not contain estrogen; they only depend on the hormone progestin to prevent ovulation. Progestin-only pills (POPs or minipills) are recommended for women who have a history of thrombosis (clotting) since estrogen significantly increases the risk of blood clots. It’s also a good option for women who don’t want to use long-term contraception. 

Despite reports that women experience fewer side effects while taking minipills, breakthrough bleeding is still possible. These pills make the uterine lining thinner, which weakens the tiny blood vessels and can cause bleeding. Also, one of the most notable side effects of progestin-only pills is irregular menstruation.

Reports estimate that 13 out of 100 users become pregnant within a year of taking POPs or minipills.

You are smoking

One of the causes of breakthrough bleeding is smoking. According to experts, women who smoke are more likely to experience bleeding while taking extended-cycle birth control pills.

Other causes of breakthrough bleeding

Besides the reasons discussed above, please note that the following can also lead to unexpected bleeding while taking oral contraceptives:

  • Diarrhea and vomiting, since they impair the absorption of the oral contraceptive pills.
  • Medications or supplements that interfere with the contraceptives. Examples include antibiotics and St. John’s wort.

Bleeding in between periods

Women who do not take birth control pills, or those who have stopped taking them, may still experience unscheduled or unexpected bleeding. The common causes of spotting between periods are:

Spotting can also be an early sign of pregnancy since implantation, the process where the fertilized egg attaches to the lining of the uterus, can cause bleeding or spotting. Similarly, light bleeding is also a warning sign of an ectopic pregnancy and miscarriage.

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When to seek medical help

If you suspect that you’re pregnant or are already in menopause, contact your doctor right away if you experience spotting. Additionally, set an appointment with your doctor if your breakthrough bleeding or spotting:

  • Lasts for more than a week
  • Becomes more severe
  • Comes with abdominal or pelvic pain
  • Is accompanied by other symptoms like dizziness and easy bruising

Learn more about Other Women’s Health Issues here


Hello Health Group does not provide medical advice, diagnosis or treatment.

Medically reviewed by

Jobelle Ann Dela Cruz Bigalbal, MD

General Practitioner

Written by Lorraine Bunag, R.N. · Updated Jan 05, 2021

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