If you think your birth control failed or you didn't use birth control, you may be feeling a little anxious, which is totally understandable. Everybody needs a plan B sometimes, especially when the stakes are high. Your plan B for preventing an unwanted pregnancy might be an emergency contraceptive (EC) pill called Plan B® One-Step, or the morning-after pill.
In the past we've covered how taking Plan B can affect your menstrual cycle. But how effective is Plan B at preventing pregnancy? In this article we'll talk about how effective it is, how to take it, and what you can expect from it. Read on to learn more or jump straight to the section most relevant to you:
How effective is Plan B?
If taken within 3 days of unprotected sex, Plan B can lower your chances of getting pregnant by 75-89%. As a general rule of thumb, time is of the essence when it comes to the effectiveness of Plan B. The sooner you take Plan B One-Step, aka the "morning-after pill," the more effective it is.
Some studies have shown that Plan B may still work for up to 120 hours, or five days, after unprotected sex. But taking it within 24 to 72 hours is definitely your best bet at preventing pregnancy. ella® is more effective than Plan B after that 72 hour mark, up to 120 hours after unprotected sex.
What is Plan B and other emergency contraception?
Emergency contraception is used as a time-sensitive way of preventing an unplanned pregnancy. The Plan B pill, ella®, and Paragard® copper IUD are three methods of EC.
Unlike birth control, EC is not meant to be used as ongoing contraception. However, EC is especially helpful to have on hand if you've missed your regular birth control pill schedule or if you're concerned about birth control failure.
Plan B One-Step
Plan B One-Step is the most common brand name for the levonorgestrel 1.5mg tablet. The same product is sold under other brand names including:
These are all emergency contraceptive pills taken by mouth once as soon as possible after unprotected sex. These are generally the easiest type of EC for most women and people who menstruate to get because they are reasonably priced and can be purchased over-the-counter.
ella morning-after pill
Another pill used for EC is called ella, or ulipristal acetate. This pill works similarly to Plan B to prevent pregnancy, and can be taken for up to five days after unprotected sex. Unlike Plan B, ella requires a prescription from your health care provider and can be more effective than Plan B if you weigh at least 155 pounds. It may not work as well in people who weigh 195 pounds or more.
Copper intrauterine device (IUD)
Paragard copper IUD is the third and most effective form of EC. Paragard is a small plastic device that is inserted into the uterus and prescribed by your health care provider. It works to prevent pregnancy if used within five days of unprotected sex. The copper from the IUD makes it much harder for sperm to get into the uterus and fertilize an egg.
If you continue to use Paragard, it can protect against pregnancy for up to 10 years as long as it stays in.
Can you still get pregnant after taking Plan B?
The timeline for a pregnancy can be difficult to predict and is different for everyone. Taking Plan B within 72 hours after unprotected sex provides you with the greatest chance of preventing pregnancy, but since it's not 100% effective, you still have a chance you may become pregnant. If your next period does not come within a week of when you are expecting it, it's a good idea to take a pregnancy test.
Keep in mind that Plan B is a medication that acts to prevent pregnancy from unprotected sex within the last 72 hours, not future unprotected sex. Plan B will not help you prevent pregnancy if you have unprotected sex after taking it nor will it terminate an existing pregnancy.
Who is Plan B for?
Plan B is for women and people who menstruate who have had unprotected sex for any reason such as failure to use birth control or not using it correctly, such as missing two or more birth control pills in a row, finding a hole in a condom, or a condom or cervical cap falling off during sex. Plan B is also for people who have experienced a sexual assault.
Some people have questions about higher BMIs and Plan B effectiveness. For those who are worried, know that the FDA says that "all women and people who menstruate, regardless of how much they weigh, can use these products to prevent unintended pregnancy following unprotected sexual intercourse or contraceptive failure."
What other factors might make Plan B less effective?
Plan B, like other medications, are most effective when used correctly. Even still, there are a few types of medications that can interact with Plan B and make it a less effective emergency contraceptive pill. These include:
Talk to your health care provider about your medication history to better understand if Plan B, or another emergency contraceptive pill, is right for you.
Additionally, to ensure maximum effectiveness, ensure you're taking Plan B within 72 hours of unprotected intercourse, while making sure the pills aren't past their expiration date or stored in extreme temperatures.
How does Plan B work?
Levonorgestrel is a progestin hormone that works by preventing ovulation. It is similar to the hormone progesterone that occurs naturally in your body. Ovulation is when an egg is released from the ovary to be fertilized by sperm. When Plan B is taken and ovulation is prevented, there is no egg released for the sperm to fertilize, and therefore no fertilized egg or pregnancy.
You may wonder whether Plan B stops an existing pregnancy. The answer is no, because that's not how Plan B works. Pregnancy does not occur immediately after unprotected sex. Fertilization and implantation must happen first, which can take days. Plan B is not an abortion pill, and if you're already pregnant, will not stop a pregnancy from occurring.
How do you take Plan B?
As soon as possible after you have unprotected intercourse, simply swallow the pill in the Plan B package. If you're taking Plan B because you missed two or more days of your normal birth control pills (BCP), continue taking the rest of your BCP as normal. In this case you will also need to use a backup method of birth control (like a condom) for the next seven days.
Side effects of Plan B are rare, but can include nausea and vomiting. If you throw up less than two hours after taking Plan B, you most likely need to take another pill. You can contact your health care provider or pharmacist for their recommendation if you're unsure whether this is necessary.
Emergency contraception should not be used as your regular form of birth control. If you are having sex regularly, there are many birth control options available to prevent pregnancy such as non-hormonal birth control and the vaginal ring.
Keep in mind that pills, IUDs, rings, implants, or shots used for birth control do NOT protect against sexually transmitted infections (STIs). It's a good idea to use a condom unless you and your partner only have sex with each other and have both been checked for STIs.
What are the side effects of Plan B?
The most common side effects of Plan B include:
Where can you get Plan B?
Since Plan B works better the sooner you take it, you can keep it on hand for future use. Everyone has to make their own choices regarding their health. If you choose not to be on a regular form of birth control, keeping Plan B handy for emergencies may be the best way to save yourself stress, anxiety, or a pregnancy.
How do you know if Plan B worked?
If you take Plan B within 72 hours after unprotected sex, your chance of becoming pregnant is low, but not impossible. The only way to know for sure whether you're pregnant is to take a pregnancy test. If your next period does not come within a week of when you expect it, it's a good idea to take a pregnancy test and contact your OB/GYN or health care provider.
Recap: How effective is Plan B?
Plan B is very effective for occasional instances where your regular birth control method fails. As long as you can take it within 72 hours of unprotected sex, or even better, within 24 hours, you have a good chance of avoiding an unwanted pregnancy.
It's smart to be prepared and have a plan in place to prevent a pregnancy that you don't want. Consider having Plan B readily available as a backup for when slip-ups happen, as they can for many women and people who menstruate.
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