It is possible to get pregnant if you missed a pill and had unprotected sex. The risk depends on your medication, how many active (hormone-containing) pills you missed, and how long it has been since your last dose.
If you miss a pill, take it as soon as you remember. Keep taking your pills according to your usual schedule. If it has been more than 48 hours since your last dose, you will need to use backup birth control. If you had unprotected sex in the five days before you resumed taking your pills, it is a good idea to use emergency contraception.
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.
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What to Do If You Miss a Birth Control Pill
Missing one pill may not increase your risk of pregnancy, depending on what type of pill you take.
- Combination pills: Many birth control pill packs have three weeks of active pills that contain either progestin and estrogen. A combination pill also has one week of placebos, which are sugar pills that have no hormones. 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.
- Progestin-only pill (mini pill): This is a pill that should be taken by mouth at the same time every day. With these packs, forgetting to take a pill if it's your first, second, or third week can affect your pregnancy risk. If you forgot a pill and have unprotected sex during this time, it is a good idea to take emergency contraception.
What to Do If You Missed a Combination 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:
One Late or Missed Combination Pill
If it's been 24 to 48 hours since your 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.
Back-up birth control may include condoms, diaphragms, or sponges.
Two or More Missed Combination Pills
If it has been 48 hours or more since your 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 the pills that are meant to be taken on days 15 to 21 (the last week of hormonal pills in a 28-day pack). 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.
What to Do If You Missed a Progestin-Only Pill
One Late Progestin-Only Pill
If it's been more than three hours since your last pill but less than a day:
- Take the late dose right away
- Use backup contraception for two days afterward
One Missed Progestin-Only Pill
If you missed an entire day:
- Take the missed pill as soon as you remember, even if that means taking two pills in one day.
- Take the rest of your pills on schedule.
- 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.
The pill is 99% effective in people who take their pill on time every day. The percentage drops to 91% in people who do not adhere to a consistent daily schedule.
Does It Matter Which Pill You Missed?
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. Missing a placebo pill doesn't.
If you miss more than one dose per pill pack, the risk of pregnancy jumps.
What Happens When You Miss a Pill
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.
The two most common side effects of missing a birth control pill are spotting and pregnancy.
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.
How Do Birth Control Pills Work?
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.
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?
If you frequently miss pills, you might consider a long-acting reversible contraception (LARC) such as an intrauterine device (IUD) or hormonal implant.
Copper IUDs do not contain hormones and can stay in place for up to 10 years. Hormone-releasing IUDs can be left in place for up to five years. Implants, such as Implanon and Nexplanon, use hormones and are placed in the upper arm. They are effective for three years.
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, backup 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.
When to Talk to a Healthcare Provider
If you miss your birth control pill often, talk to your healthcare provider about an alternate contraception that does not need to be taken daily. For example, you may want to consider using a birth control patch or IUD.
You should also see your healthcare provider if you have had a positive pregnancy test, or if you have any early signs of pregnancy such as:
- A missed period
- Nausea and vomiting that does not seem to be related to an illness or something you ate
- Breast tenderness/breast enlargement
- Frequent urination
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.
Many people wonder whether emergency contraception can cause an abortion if pregnancy has already occurred. Emergency contraceptive pills will not be effective if implantation of a fertilized egg has occurred. They can not cause abortion. Copper IUDs are only implanted if a high-sensitivity pregnancy test is negative.
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.
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.