Can I Get Pregnant If I Miss a Birth Control Pill?

In short, yes—you can get pregnant if you miss one pill. But the risk depends on your medication, how many active (hormone-containing) pills you missed, and how long it has been since your last dose.

Missing one active combination (estrogen+progestin) birth control pill slightly increases your odds of pregnancy, but not by a whole lot. Some level of medication will still be in your system even when you miss an active pill or take it at the wrong time.

If you take the mini-pill—which contains progestin but not estrogen—your chances of getting pregnant after missing an active pill are greater, but it still isn’t likely.

However, if you miss more than one dose per pill pack, the risk of pregnancy jumps. Missing a placebo pill doesn't affect your pregnancy risk.

This article discusses the likelihood of pregnancy after forgetting to take birth control pills one or more times in a cycle. It also details how timing and other things can interfere with the pill's effectiveness.

What Happens When You Miss a Pill

Oral contraceptives provide your body with just enough hormones to block ovulation. Ovulation, when an egg is released from the ovaries, usually occurs between day 11 and day 21 of the menstrual cycle. People are most fertile during the two to three days before ovulation.

When you take your birth control pills as prescribed, your body will have a steady supply of medication to keep you from ovulating. This is referred to as "maintaining the therapeutic drug level," or how much of the drug needs to be in your system to be effective.

The birth control pill is not 100% effective even when taken perfectly. To achieve the best results, you need to take the pill at the same time every day. Missing or delaying doses allows the therapeutic drug level to drop.

• Over the course of an hour, the drop may not be significant.
• Over 24 hours, the drop could be very significant.

Ultimately, there is a point at which drug levels drop low enough that ovulation can occur. This can happen more quickly in some people than others, and the drop is faster with the progestin-only mini-pill use versus combination pill use.

Vomiting or diarrhea can also lessen the pill's effects because too much active drug may be eliminated from the body. The effect can be similar to forgetting to take the pill altogether.

Does It Matter What Pill You Miss?

Many birth control pill packs have three weeks of active pills that contain either progestin and estrogen (combination pills) or only progestin. They also have one week of placebos, which are sugar pills that have no hormones.

With these packs, forgetting to take a pill if it's your first, second, or third week can affect your pregnancy risk. Forgetting to take a placebo pill does not affect your pregnancy risk, as these pills are only there to help you remember to take a pill each day.

There are also packs with 24 active pills and four placebos or 84 active pills and seven placebos. You can determine whether a missed pill is a concern by applying the same knowledge—a missed active pill affects your risk, while a missed placebo does not.

What to Do If You Miss a Pill

Planned Parenthood has a handy quiz you can take to figure out what to do in your specific situation, but here's a review of the general guidelines:

1 Late or Missed Combination Pill
(24 to 48 hours since last dose)

• Take the dose as soon as possible. This might mean doubling the dose if you missed an entire day.
• Continue your pill pack as scheduled.
• No backup contraception is needed.

2 or More Missed Combination Pills
(48 hours or more since last dose)

• Take the pill you most recently missed as soon as possible, even if that means taking two pills in one day. Do not take any other missed doses.
• Continue your pill pack as scheduled unless you missed pills meant to be taken on days 15 to 21. In that case, finish your active pills, skip your placebos, and start a new pack.
• Use backup birth control or avoid sex until you've taken active pills for seven days in a row.

1 Late Progestin-Only Pill
(More than three hours late; same day as original dose)

• Take the late dose right away.
• Use backup contraception for two days afterward.

1 Missed Progestin-Only Pill
(Missed entire day)

• Do not take the missed dose the next day.
• Use backup birth control for one week.

Call your healthcare provider's office if you are unsure how to proceed or need further assistance. You can also check your birth control package insert for more information.

Emergency Contraception

If you missed a pill and had unprotected sex before realizing you missed a pill, you might consider using emergency contraception. The most common forms of emergency contraception are the copper IUD or the morning-after pill.

Copper IUD

The most effective emergency contraception is insertion of a copper intrauterine device (IUD). It is effective up to five days after unprotected sex. It involves a healthcare provider inserting a T-shaped copper device into the uterus.

The IUD will prevent pregnancy with more than 99% effectiveness. It can be inserted up to five days after unprotected sex, although some studies suggest it can be inserted even later, as long as high-sensitivity pregnancy tests are negative.

The Morning After Pill

Emergency contraception pills are another option. They are commonly called the morning after pill. There are two main types of morning after pills.

Levonorgestrel: One type contains the hormone levonorgestrel includes a hormone-containing pill. Brands include Plan B One Step, Take Action, My Way, and others. It can be used up to three days after unprotected sex. The levonorgestrel pill might not be as effective in people who weigh more than 165 pounds. It is available over-the-counter in most pharmacies.

Ulipristal acetate: Pills containing ulipristal acetate are considered more effective than levonorgestrel pills. They work best in people who weigh less than 195 pounds. The brand name for this pill is Ella. Ella requires a prescription. It can be taken up to five days after unprotected sex.

Preventing a Missed Pill

Try to identify why you missed your dose:

• Was it caused by a change in your schedule?
• Was there an event or incident that distracted you?
• Are the pills out of sight, out of mind?
  
• Are you supposed to take your pill at a time you have lots of other things to do?

By pinpointing the cause, you can take steps to avoid missing a pill in the future. For example:

• Set the alarm on your cell phone to remind you when to take your pill.
• Move your pack to, say, your desk instead of keeping it in your medicine cabinet.
• Once you finish your current pack, change when you take birth control. Combination-pill users can choose any new time without issue. If you use a progestin-only pill and there is more than a three-hour difference between the current dose time and the desired one, back-up birth control should be used for two days after making the switch.
  

Neuroscientists who study habit formation recommend tying habits together—such as taking your birth control pill right after you brush your teeth.

This technique, known as habit stacking or habit chaining, has been shown to increase the likelihood that a new habit will stick.

Summary

Taking birth control every day, at the same time each day, is the best way to prevent pregnancy. A steady supply of hormones will keep you from ovulating. However, don't panic if you forget. You may still have some level of protection.

Be sure to resume your birth control according to the specific instructions for your medication.

If you had unprotected sex and want to prevent pregnancy, you may want to consider using emergency contraception.