How long does Plan B stay active in your body?

Key takeaways

• Plan B contains levonorgestrel, which can stay in your system for up to 6 days, but its effectiveness in preventing pregnancy does not last that long.
• For the best chance of preventing pregnancy, Plan B should be taken as soon as possible, but no later than 72 hours after unprotected sex.
• While Plan B is a safe option for emergency contraception, it shouldn’t be used as a regular birth control method because it’s less effective and may cause irregularities in your menstrual cycle.

—————-

Need a diagnosis or prescription quickly? Optum Perks offers personalized on-demand care in as little as 15 minutes. For $29, answer a few questions online and receive a diagnosis and treatment plan from a US-licensed healthcare professional. Get started here.

Overview

Plan B One-Step is a brand-name drug that’s used for emergency contraception. It’s often called the morning-after pill, and you can buy it over the counter (OTC) without a prescription. It contains 1.5 milligrams (mg) of levonorgestrel.

Some people may also use the name “Plan B” colloquially to refer to other emergency contraception pills.

Taking Plan B within 72 hours after having sexual intercourse lowers the chance of unintended pregnancy if you:

• aren’t using any form of birth control
• are using birth control but it didn’t work, like if a condom broke
• missed a birth control pill or incorrectly used other forms of birth control

How long does Plan B stay in your system?

The average half-life of Plan B is 27.5 hours. This is how long it takes your body to use and reduce the total dose of the drug by half. This half-life may be the most potent and effective time period for the drug.

On average, your body removes Plan B after about five half-lives, which is just under 6 days. Keep in mind that the half-life of a medication can vary from person to person, and Plan B could stay in your body for a slightly longer or shorter period of time than 6 days. 

Even if some Plan B dose stays in your system for 6 days, this doesn’t mean it’s effective at preventing a pregnancy for that time.

For example, if you took a Plan B pill 4 days before having sex without birth control, it may no longer prevent pregnancy.

When should you take Plan B? 

The sooner you take Plan B after having sex without birth control, the better it works. 

You should take Plan B no later than 72 hours, or 3 days, after having sex without a barrier method or another birth control method. If you take Plan B within this time frame, your chance of getting pregnant is reduced by up to 89%.

If more than 72 hours have passed, you may need other emergency contraception options, including other types of pills and intrauterine birth control devices (IUDs).

Be sure to discuss these options with a healthcare professional.

How long do Plan B side effects last?

Like any medication, Plan B may lead to side effects, including:

• nausea
• vomiting
• stomach pain
• fatigue (low energy)
• tender breasts 
• spotting and changes in menstrual bleeding
• headache
• dizziness 

Plan B and other progestin medications may also increase the chance of an ectopic pregnancy. This is when a fertilized egg implants and grows outside the uterus. It can lead to serious health complications.

If you experience stomach pain, nausea, lightheadedness, or unusual vaginal bleeding for 3 to 5 weeks after taking Plan B, it’s important to get immediate medical care. 

However, serious side effects from Plan B are rare, and side effects you do see are likely to be mild and short-lived.

Another thing to consider is that Plan B is not always effective, even if you take it within the recommended time frame. If your period is late after taking Plan B, consider taking a pregnancy test. 

While Plan B is safe for most people, it’s best to talk with a healthcare professional before taking it if you:

• are taking medications or herbal products that include enzymes that metabolize progestins, such as topiramate, St. John’s wort, and phenytoin
• are taking medications for HIV
• think you might be pregnant
• are nursing

How does Plan B work?

Levonorgestrel, the active ingredient in Plan B One-Step, is a synthetic progestin hormone. Progestin mimics your body’s natural progesterone hormone — which affects your menstrual cycle and pregnancy.

The 1.5 mg of levonorgestrel in Plan B prevents the ovaries from releasing an egg. It also thickens your cervical mucus, making it more difficult for sperm to reach the egg.

This makes it less likely that a pregnancy will occur, though it doesn’t work 100% of the time.

Plan B isn’t an abortion pill and won’t terminate an existing pregnancy. It also doesn’t protect against sexually transmitted infections (STIs).

How often can you use Plan B?

There isn’t a limit on how many times you can use Plan B. While it is a safe and effective option for emergency contraception, you should not rely on it as a regular method of birth control. It’s not as effective as other birth control options like the pill, condoms, or IUDs. 

Also, regularly using emergency contraception may make your menstrual periods irregular and increase the chance of side effects, including hormone-related disorders.

Plan B alternatives

Other brand names for levonorgestrel emergency contraception include:

• Fallback Solo
• Next Choice One Dose
• Opcicon One-Step
• AfterPill
• EContra One-Step

Another emergency pill option is ulipristal acetate (Ella). It may be more effective than Plan B at preventing pregnancy after 3 to 5 days. But it’s not available OTC, so you need a prescription from a healthcare professional to get it.

Besides pills, a copper IUD can also work as emergency contraception. Getting one within 5 days after sex without birth control may reduce the chance of pregnancy by 99.9%. Plus, the IUD provides ongoing protection, so you won’t need to use Plan B later.

Nonemergency hormonal birth control methods include:

• Progestin-only pills (mini-pills): You take one pill every day. Options include norethindrone (Camila).
• Birth control injection: You use it as an injection every 3 months. Options include medroxyprogesterone acetate (Depo-Provera).
• Birth control ring: You insert it into the vagina. Options include etonogestrel ethinyl estradiol (NuvaRing).
• Birth control patch: The patch goes on your skin and it releases hormones into the bloodstream. Options include ethinyl estradiol norelgestromin (Xulane).
• Implant: A tiny rod is inserted under your skin. Options include etonogestrel (Nexplanon).

————-

If you need help covering the cost of medications, the free Optum Perks Discount Card could help you save up to 80% on prescription drugs. Plus, you can now get them delivered to your home in as little as 3 days. Search for your medication here.

Summary

Plan B may stay in your system for 5 to 6 days, but it won’t be effective at preventing pregnancy for all that time. The drug’s half-life is around 27.5 hours, which is likely its most effective time period.

Even if you take Plan B within 72 hours, you may still get pregnant. Plan B does not protect against STIs and is not suitable as a regular birth control method.

Talk with a healthcare professional for personalized guidance if you think you might be pregnant or if you need other emergency contraception options. 

—————

Download the free Optum Perks Discount Card to save up to 80% on many prescription medications. Plus, you can now get them delivered to your home in as little as 3 days. Search for your medication here.