How long does Plan B stay in your system?
While there are different types of birth control out there, emergency contraceptives, like Plan B, come to the rescue when you need them the most. Whether you’ve recently taken Plan B or you’re wondering (for future “uh-oh” moments) how long its side effects can last, you may be asking yourself: how long does Plan B stay in your system?
The short answer: it depends. Typically, most bodies take between 24 and 26 hours to reduce the hormones in a single pill of levonorgestrel (better known as Plan B) by 50%. However, it takes longer for your excretory system to completely dispel Plan B, and you may notice side effects in the meantime.
In this guide, we’ll discuss Plan B’s life cycle in your body, factors that can influence how long it sticks around, and how effective this pill is in comparison to other emergency contraceptives.
How long does Plan B stay in your system?
The condom slipped off, the pills forgotten in a medicine cabinet, you couldn’t squeeze in your usual hormone shot between shifts…whatever the scenario, Plan B, also known as the morning-after pill, can be a reliable means of preventing pregnancy if your usual method falls short.
That said, this option is regarded as an emergency contraceptive, partly because of the hormonal punch it packs—and the amount of work it takes for your hormones to normalize after taking it.
Levonorgestrel falls under a cluster of medications called progestins, a synthetic form of progesterone. And while progestins have been used in contraceptives like “the Pill” for decades, Plan B and other emergency birth control methods disperse it in ultra-high doses.
Progestins work to prevent pregnancy in three ways:
It makes the uterine wall less thick and cozy for any fertilized egg attempting to embed there.
Prevents the ovaries from releasing an egg by slowing the production of luteinizing hormone (LH).
Prevents sperm from fertilizing an egg by thickening the cervical mucus, which makes it difficult for sperm to swim through.
Using a multi-pronged approach, Plan B is a highly effective way of preventing pregnancy 24 to 72 hours after a slip-up. But what happens after you’ve taken plan B? How long does this hefty dose of hormones take to run their course in your body?
What is a half life?
In medicine, a half life refers to the amount of time it takes a medication to lose half of its original concentration in your system. The term is typically used to describe how long a drug will stay in your body before it’s completely eliminated by your body’s natural detoxification and excretory system (thank you, kidneys and liver!).
Plan B’s half life is typically 24 to 32 hours. This means that, in most individuals, it takes 24 to 32 hours for the progestin it delivers to your body to drop to half its original level.
Its entire “lifespan” is highly contingent on how quickly it can be eliminated from the body, as it must go through several metabolic processes before it hits the liver.
After it reaches its half life, there are two other milestones in the life cycle of a Plan B pill:
Up to 5 days (120 hours) – Approximately 94 to 97% of Plan B’s potency will have dissipated after four to five half lives. This means Plan B typically continues to “work” in the body for approximately five days after you’ve taken it, and can still be moderately effective up to 120 hours after having unprotected sex.
An average of 7 days – Typically, your excretory system will completely remove Plan B from your body within 7 days after taking it. However, this depends on a host of variables, which we’ll jump into shortly.
While Plan B itself typically leaves the body in a week, you may be concerned about the potential side effects that accompany it. Many people who take Plan B will experience side effects like nausea, fatigue, or emotional distress, but these typically fade around day 4 or 5 after ingesting it (even if progestin is still in your system). In most individuals, side effects diminish within a few days. However, it's best to keep an eye on these Plan B side effects. In some cases, these may be signs that Plan B didn't work after unprotected sexual intercourse.
Variables that influence how long Plan B stays in your system
Everyone’s physiology is unique: two over-the-counter painkillers might crush your stress-induced headache immediately, but they may fail to make a dent in your BFF’s.
Similarly, the amount of time Plan B emergency pill remains in your body is influenced by several factors, including:
Age – The younger you are, the faster Plan B could be flushed out of your system. Age may impact the speed at which your circulatory system works and getting Plan B’s progestin to your liver and kidneys—two of the main organs involved in eliminating the substances obtained through medication.
Genetics and metabolism – Both genetics and metabolism play a role in how swiftly you process medications. The function of specific enzymes and proteins in the body differs from individual to individual, and can either accelerate or delay the length of time Plan B lingers around. If you have a generally slower metabolism, it may take longer for your body to completely eliminate Plan B.
Liver function – As one of your body’s biggest detoxifiers, your liver plays a fundamental role in how long Plan B stays in your system. People who have impaired hepatic function—whether due to liver disease or another cause that could prevent it from operating at capacity—may have to wait longer for Plan B to be eliminated from the body.
Kidney function – Like the liver, your kidneys play a key role in your body’s detoxification system. If you’ve ever struggled with kidney disease or a condition that affects them, this can prolong the time it takes for your body to process medications.
Dosage – Plan B is a single pill designed for contraception failure or other “heat of the moment” circumstances. You should never take more than one dose of Plan B in the hopes it will further reduce your likelihood of becoming pregnant. Furthermore, taking more than the recommended dose of Plan B (1 pill) means that it will take your body longer to get rid of it.
Just note that the Plan B emergency contraceptive pill is not meant to serve as your primary and regular birth control method. So you may be wondering, can you take Plan B on birth control? In fact, yes. It's best if used in addition with your regular birth control.
How effective is Plan B?
The Plan B pill is remarkably effective at preventing pregnancy. Research shows that it prevents 7 out of 8 pregnancies when taken within a 72-hour window after an unprotected sexual encounter. Other research suggests that it may even be effective up to 120 hours after unprotected sex.
Even better? Plan B isn’t the only emergency contraceptive available. And because it’s always great to have options, here are two other emergency contraceptives that can help you steer clear of pregnancy following a slip:
ella – While they may be similar, there are a few differences between Ella vs. Plan B. Unlike Plan B, which relies on high levels of progestin to work, ella uses ulipristal acetate (UPA)—an antiprogestin emergency contraceptive. Like Plan B, ella also works to prevent ovulation. This method reduces your chances of getting pregnant by 85% if it’s taken with 5 days of unprotected sex, and it’s more effective than Plan B at preventing pregnancy up to 120 hours after. To gain access to ella, you’ll need to get a prescription from your healthcare provider.
Copper intrauterine device (IUD) – A copper IUD, which you may recognize as a ParaGard, is a T-shaped copper instrument that can be inserted into the uterus up to five days after unprotected sex to decrease your chances of getting prgnant. Copper IUDs work to prevent pregnancy due to the substance they’re made of: copper is a metal that repels sperm.
Getting an IUD will require an appointment with your healthcare provider, as they’ll be the ones who insert it for you to ensure its efficacy. When used properly, copper IUDs can remain inside you for up to 10 years to prevent pregnancies. According to some studies, copper IUDs are one of the most effective forms of emergency contraception available today.
Find a contraceptive plan with Favor
From a broken condom to a missed dosage of your birth control pill–and from no viable contraception in sight to forgetting to schedule your Depo–there are just as many reasons for the potential of an unintentional pregnancy as there are factors that contribute to how long Plan B stays in your system.
Age, genetics, liver function–all affect the amount of time Plan B may hang around and, in some cases, cause side effects. And yet, between its effectiveness and the tremendous sense of comfort it can offer, Plan B is a sound, safe option for those “uh oh” moments.
Favor is your trustworthy friend in times just such as these. Not only do we have a wide range of birth control options–should you choose that route–but we also supply emergency contraceptives (ECs) with free delivery, complete with self-care extras and in a discreet package to boot. With Favor, you can shift from emergency mode straight into “I’ve got this handled.”
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