What is breakthrough bleeding?
Breakthrough bleeding is any unscheduled vaginal bleeding or spotting that occurs while taking hormonal birth control. This is different from the planned "withdrawal bleeding" that happens during the placebo week of a standard 28-day pill pack, when hormone levels drop. On hormonal contraception, the synthetic hormones estrogen and progestin work to thin the uterine lining (endometrium) to prevent a fertilized egg from implanting. In some cases, the uterine lining becomes unstable and can shed irregularly, leading to spotting.
Common causes of bleeding on the pill
Several factors can contribute to breakthrough bleeding, ranging from simple user error to the specific formulation of the birth control pill itself.
Inconsistent pill use
This is one of the most common causes of breakthrough bleeding. Missing a pill, taking it late, or experiencing severe vomiting or diarrhea can cause a sudden drop in hormone levels. This fluctuation can lead to the premature shedding of the uterine lining, resulting in spotting. This is especially true for progestin-only pills, which must be taken within a very narrow timeframe each day to remain effective.
Starting or switching a new pill
When you begin a new birth control pill or switch to a different brand, your body needs time to adjust to the new levels of hormones. Irregular bleeding is most common during the first three to six months and often subsides as your body adapts.
Type of pill and hormone dosage
The specific composition of your birth control pill can affect your likelihood of experiencing breakthrough bleeding.
- Low-dose estrogen pills: These pills contain a lower dose of estrogen (less than 30 mcg of ethinyl estradiol) and are more likely to cause spotting than higher-dose pills.
- Progestin-only pills: Also known as mini-pills, these are more frequently associated with irregular bleeding than combined pills, with up to 70% of users experiencing it at some point.
- Continuous-cycle or extended-cycle pills: These formulations reduce or eliminate the hormone-free week, which can lead to more frequent breakthrough bleeding, particularly in the initial months. Over time, however, the incidence of bleeding tends to decrease.
Other medications or supplements
Some medications and herbal supplements can interfere with how your body metabolizes the hormones in your birth control pill, which can lead to breakthrough bleeding and reduced contraceptive effectiveness. Examples include the antibiotic rifampin and the herbal supplement St. John's Wort. It is always best to check with your doctor or pharmacist when starting any new medication.
Lifestyle factors
Lifestyle choices can also play a role in bleeding irregularities.
- Smoking: Studies show that women who smoke are more likely to experience breakthrough bleeding compared to non-smokers.
- Stress, weight changes, and illness: Significant changes in your body due to stress, weight fluctuations, or a temporary illness can also cause hormonal shifts that trigger spotting.
Comparing pill types and breakthrough bleeding
| Pill Type | Hormone Composition | Typical Bleeding Pattern | Frequency of Breakthrough Bleeding | Effectiveness on Schedule | When Bleeding Stabilizes |
|---|---|---|---|---|---|
| Combined (Standard 28-day) | Estrogen + Progestin | Regular withdrawal bleeding during placebo week | High in first 3-6 months; decreases over time | Very effective with consistent use | Usually within 6 months |
| Combined (Low-dose Estrogen) | Lower dose of Estrogen + Progestin | Regular withdrawal bleeding, potentially lighter | More common than with standard combined pills | Very effective with consistent use | Usually within 6 months |
| Progestin-only (Mini-pill) | Progestin only | Irregular periods, spotting, or no period at all | High in first few months; can decrease over time | Requires very strict, same-time daily use | Highly variable, may always be irregular |
| Extended/Continuous-cycle | Estrogen + Progestin (no placebo week) | No withdrawal bleeding, but higher chance of breakthrough bleeding | High in first 3-6 months; decreases significantly | Effective with consistent, continuous use | Usually within 6 months or after a scheduled break |
What you can do to manage bleeding
If you are experiencing frustrating breakthrough bleeding, there are several steps you can take:
- Stay consistent: Take your birth control pill at the same time every day to keep hormone levels stable. If using a progestin-only pill, adhering to the narrow time window is especially crucial.
- Track your bleeding: Keep a diary or use a period-tracking app to monitor your bleeding patterns. This can help you and your doctor identify triggers and determine if the bleeding is becoming less frequent over time.
- Try a scheduled break: For those on continuous-cycle pills who have taken active pills for at least 21 days, a healthcare provider might suggest a three-day hormone-free break to allow for a withdrawal bleed.
- Consider a different pill: If bleeding persists after six months, talk to your doctor about switching to a pill with a different estrogen dose or progestin type.
- Address lifestyle factors: If you smoke, quitting can help reduce breakthrough bleeding. Managing stress through mindfulness, exercise, and proper nutrition can also help stabilize hormones.
When to see a doctor
While breakthrough bleeding is often harmless and temporary, it's important to consult a healthcare professional to rule out other medical concerns, especially if the bleeding is prolonged, heavy, or accompanied by other symptoms. You should see a doctor if:
- Breakthrough bleeding lasts for more than six months after starting or switching a pill.
- You experience heavy bleeding that soaks through a pad or tampon within an hour or two.
- Bleeding is accompanied by severe abdominal pain, fever, or signs of a blood clot.
- You have other concerning symptoms or suspect an infection or pregnancy.
A doctor can perform an evaluation to rule out conditions such as sexually transmitted infections (STIs), uterine fibroids, or cervical polyps.
Conclusion
Understanding why you keep bleeding on your birth control pill is the first step toward managing it effectively. For most, breakthrough bleeding is a common, temporary side effect as the body adjusts to hormonal changes. Factors like inconsistent pill use, the type of pill, and lifestyle can all contribute. However, if bleeding persists beyond a few months, is heavy, or is accompanied by other symptoms, seeking medical advice is important to ensure it is not caused by an underlying health issue. By maintaining a consistent pill schedule, monitoring your body's response, and communicating with your healthcare provider, you can find the right balance for your contraceptive needs.
