Taking the birth control pill comes with many bonuses. There’s the biggie (preventing an unwanted pregnancy), but it can also help with painful, heavy, or long periods, relieve miserable menstrual cramps and PMS, and, depending on the type, even prevent acne, among other things.

Some hormonal birth control completely stops your period while others allow for a monthly cycle, but all kinds can cause annoying side effects for some people, typically in the first few months after you start taking it. One super common one? Breakthrough bleeding—or spotting when you don’t have your period. It’s usually nothing to worry about, but it can be unpredictable and inconvenient (who wants to see a random red streak in their underwear?).

Here, Stephanie Hack, MD, FACOG, a board-certified OB/GYN and founder of Lady Parts Doctor, explains why you might bleed between periods when you’re on the pill (and other forms of hormonal birth control), how long it can last, and how to make it stop ASAP.

8 causes of breakthrough bleeding while on the pill

A lot of things can cause irregular bleeding when you take the pill. Here are some of the most common:

1. Forgetting to take your pill

We’ve all been there: Suddenly it’s Friday, and after a dizzying week, you realize you’ve forgotten to take your pill the past few days. But skipping the pill is a recipe for breakthrough bleeding because it can screw with your hormones. Even “not taking your birth control pill at the same time every day can lead to hormone fluctuations, which might result in breakthrough bleeding,” says Dr. Hack. “This is especially true for progestin-only pills, where even a few hours’ delay can significantly affect their effectiveness,” she adds.

“Not taking your birth control pill at the same time every day can lead to hormone fluctuations, which might result in breakthrough bleeding.”—Stephanie Hack, MD, OB/GYN

2. Your body’s adjusting to a new pill

Just started a new type of birth control? You might notice some spotting. Breakthrough bleeding can happen as your body adjusts to the hormones, or your uterus transitions to a thinner lining (aka, endometrium), according to the Mayo Clinic.

3. You have unstable endometrial tissue

Birth control can often help reduce pelvic pain in people with endometriosis—a condition that causes tissue similar to the lining of the uterus to grow outside the uterus, per the Mayo Clinic. But the pill can also lead to breakthrough bleeding. “The shedding of unstable endometrial lining can cause spotting,” Dr. Hack says. “This occurs as the endometrium reacts to the hormonal changes induced by the pill.”

4. Pregnancy

If you take oral contraceptives (aka, the pill), odds are you’re trying to prevent a pregnancy. But “it’s possible to get pregnant while on the pill if you miss pills or don’t take them correctly,” Dr. Hack says. Yep, whenever you don’t take birth control (or any medicine) as prescribed, the drug can become less effective. In this case, it can lead to an unplanned pregnancy. “Pregnancy can cause spotting or bleeding, which might be mistaken for breakthrough bleeding,” says Dr. Hack. This type of bleeding is often called implantation bleeding, and only happens for a short time right when you get pregnant, per the Mayo Clinic.

5. Other medications

Your breakthrough bleeding might be linked to other meds in your pillbox. “Certain medications, including some antibiotics, anti-seizure medications, and herbal supplements, can reduce the effectiveness of birth control pills, potentially leading to breakthrough bleeding,” Dr. Hack says. If you’re on the pill and have to take other medications, talk to your doctor about potential interactions, and whether you’ll need a backup method of birth control in the meantime.

6. Underlying medical conditions

Sometimes an underlying health issue (that’s unrelated to birth control) can make you bleed between periods. For example, “conditions like sexually transmitted infections (STIs) can cause inflammation, irritate the cervix, and cause bleeding or spotting,” says Dr. Hack. Abnormal growths like uterine fibroids can also lead to irregular bleeding, according to the American College of Obstetricians and Gynecologists (ACOG). If you think your breakthrough bleeding stems from an underlying issue (like a hormone imbalance, for example), talk to your OB/GYN, who can run some tests and treat the underlying issue.

7. You’re vomiting or have diarrhea

If you catch a stomach bug, and (unfortunately) have stuff coming out both ends, you might get some breakthrough spotting. Vomiting and diarrhea “can interfere with the absorption of the pill, reducing its effectiveness and possibly leading to breakthrough bleeding,” says Dr. Hack. This will often resolve once you’ve healed from the bug.

8. It’s a more common side effect with certain types of pills

While bleeding between periods can happen with any birth control pill, it’s more likely with certain types. Case in point: Spotting is common with low-dose and ultra-low-dose birth control pills, the implant, and hormonal intrauterine devices (IUDs), according to ACOG.

Who’s most likely to get breakthrough bleeding on the pill?

Certain people are more prone to breakthrough bleeding. The following creates a higher risk of spotting between periods, per ACOG and the Mayo Clinic:

• If you take certain medications (like emergency contraception pills), antibiotics, or supplements (such as St. John’s wort)
• If you smoke cigarettes
• If you don’t take your birth control pills consistently
• If you have certain infections, such as chlamydia or gonorrhea
• If you use birth control pills, or the vaginal ring, and take a continuous dose of hormones to skip your periods altogether
• If you have benign (not cancerous) growths such as uterine fibroids

You’re also more likely to have irregular bleeding when you first start taking the pill. Remember, it can take time for your body to adjust to the hormones. But “breakthrough bleeding can occur even after years of being on the pill,” Dr. Hack says. “This might be due to changes in your body, interactions with other medications, or even just sporadic hormonal fluctuations.”

How long does breakthrough bleeding last?

When you first start a hormonal birth control pill, it can be normal to spot for a bit. But breakthrough bleeding usually subsides within two to three months once your body gets used to the new hormones, according to Planned Parenthood. Keep in mind, though, if you skip your hormone-free week and take the pill continuously (to avoid or delay your period), you’re more likely to have irregular bleeding, even after the first few months.

With other kinds of birth control, you might bleed between periods a little longer.  Spotting after getting an IUD inserted might linger longer (usually resolving within six months), but if you have the implant, whatever bleeding you get in the first three months is typically what you can expect for future periods, according to ACOG.

Treatment for breakthrough bleeding from the pill

Breakthrough bleeding is incredibly common, especially during the first few months of taking hormonal birth control. Though it’s usually temporary, irregular bleeding can be irritating (it’s not fun to find blood on your underwear when you least expect it). Luckily, there are some things you can do to make it stop sooner rather than later. Here are a few tips, per ACOG and the Mayo Clinic:

• Track breakthrough bleeding: While this won’t make it stop, tracking your pattern of breakthrough bleeding can reassure you that it’s decreasing over time. It may also be helpful to note your period blood color (breakthrough bleeding is usually light pink/red) and consistency when tracking.
• Quit smoking: Smokers are more likely to get breakthrough bleeding than nonsmokers.
• If you get continuous hormones with the pill or vaginal ring, take a hormone-free break and schedule a period every few months: This gives the uterus a chance to shed any built-up lining, which can help reduce irregular bleeding.
• Take your birth control pills at the same time each day: This will reduce your risk of your hormones getting thrown off, which can lead to irregular bleeding.
• Take ibuprofen (or other OTC pain relievers): This can be helpful for pain from IUDs, implants, or the birth control shot.
• Talk to your OB/GYN: Your doctor may suggest different options to make things better. For example, you can switch from an ultra-low-dose birth control pill to a low-dose pill, change the number of placebo (or pill-free) days, or try other methods of birth control.

When to see a doctor

Usually, breakthrough bleeding is a harmless (albeit annoying) side effect of hormonal birth control. But sometimes spotting or bleeding between periods can be a sign of something else that warrants a visit to your doctor. “You should consult your doctor if breakthrough bleeding is heavy, accompanied by pain, occurs after sex, or persists beyond a few menstrual cycles,” says Dr. Hack.

“It’s also important to seek medical advice if you experience other symptoms like severe pelvic pain, unusual discharge, dizziness, or fatigue, as these could indicate a more serious condition,” she adds.

FAQ

Can stress cause breakthrough bleeding on the pill?

“Stress can affect your body in various ways, affecting your hormone levels and therefore your menstrual cycle,” says Dr. Hack. So, in theory, it’s possible for stress to cause spotting between periods. “However, the primary causes of breakthrough bleeding are usually related to the factors [previously] mentioned,” she says.

Can you get pregnant during breakthrough bleeding on the pill?

Yep. If you have bleeding because you missed pills, you’re sick with a stomach bug, or you’re taking a medication that interacts with your birth control, the pill might be less effective, says Dr. Hack. And when the pill doesn’t do its job like it should, you can get pregnant. The takeaway: If you’re not planning on having a baby, “it’s important to use contraception consistently and correctly to prevent pregnancy,” she says. This could mean using condoms or other barrier method until you’re feeling better and the bleeding has stopped.

—medically reviewed by Andrea Braden, MD, OB/GYN