How Late Can Your Period Be After Taking Plan B One-Step?

Plan B One-Step is a single-dose emergency contraceptive (EC) pill. It contains the active ingredient levonorgestrel, a synthetic hormone belonging to the progestin class. Plan B One-Step and its generic alternatives are available over the counter (OTC). 

The Food and Drug Administration (FDA) has approved the use of Plan B One-Step to reduce the chance of pregnancy if taken within three days (72 hours) after unprotected sex.

Plan B One-Step is intended for use if another contraceptive method fails (such as a condom breaking during sex) or isn’t used.

Taking Plan B One-Step may affect your period. Some people get their period about a week early or a week late after taking Plan B One-Step, and their bleeding may be lighter or heavier than usual. However, if your period is more than a week late, you could be pregnant.

Keep reading to learn more about the link between taking Plan B One-Step and your period's timing, along with basic safety and dosage information regarding its use.

Understanding the Morning-After Pill

Emergency birth control such as the morning-after pill, can help decrease your chance of becoming pregnant after unprotected sex. EC pills, like Plan B One-Step, work by preventing ovulation, the release of an egg from the ovaries.

By stopping this process, the sperm cannot fertilize the egg, thus avoiding a pregnancy.

It is important to note that EC will not have any impact if ovulation has already taken place. As a result, EC does not affect fertilized eggs or pregnancies already implanted.

EC, including Plan B One-Step, differs from Mifeprex (mifepristone). Mifeprex is a medication given in combination with the drug misoprostol for medical termination of a pregnancy up to 70 days into the pregnancy.

EC, on the other hand, only works as a preventive measure against pregnancy, with no effect after pregnancy begins.

Some states restrict access or completely disallow the use of Mifeprex. Fourteen states have banned access to Mifeprex for medical termination of pregnancy, while another 15 states limit its use to certain situations.

In contrast, Plan B One-Step is legal and available in all 50 states.

What Is Plan B One-Step?

The FDA approves Plan B One-Step to reduce the likelihood of pregnancy following unprotected sex. It comes as a single-dose oral tablet that you swallow. It is intended for use in people of reproductive age. 

Plan B One-Step works up to 72 hours after unprotected sex to prevent pregnancy. Taking it as soon as possible increases its effectiveness and reduces the chances of getting pregnant.

The sooner you take it after sex, the more effectively it works, though some research suggests that it may still work up to four days (96 hours) afterward.

Levonorgestrel, the active ingredient in Plan B One-Step, is also available OTC as several other emergency contraceptive products, such as Her Style, Opcicon One-Step, and Fallback Solo.

Levonorgestrel is also an active ingredient found in other contraceptives, such as certain types of birth control pills, transdermal patches, and intrauterine devices (IUDs).

How Does Plan B One-Step Work?

Plan B One-Step prevents or delays ovulation when the ovary releases an egg. As a result, sperm cells cannot reach or fertilize the egg, which helps prevent pregnancy.

Plan B One-Step works by preventing or delaying ovulation. If you take it after ovulation has already occurred, it may be less effective.

However, since you may not know when you ovulated, you can still take Plan B One-Step at any time during your menstrual cycle to help prevent pregnancy within three days after having unprotected sex.

Note that it offers no protection against HIV (human immunodeficiency virus) or other sexually transmitted infections (STIs). Therefore, it should not be considered a preventative measure against STDs.

Your Period & Plan B One-Step

Taking Plan B One-Step may result in changes to the menstrual cycle. After taking Plan B One-Step, your period may be earlier or later than expected. In most cases, individuals taking it will get their period within a week when expected.

However, if your period is more than a week late, this could be a sign of pregnancy; take a pregnancy test or talk to a healthcare provider for guidance.

Period flow and duration may be similarly affected by Plan B One-Step. Some individuals experience heavier or lighter bleeding than usual, and their period may be longer or shorter than usual. 

Some people may notice spotting or light bleeding after taking Plan B One-Step, but this side effect may not be your actual period. You should still anticipate your period within a week before or after the expected time.

After taking Plan B, you may feel anxious while waiting to see if it was successful at preventing pregnancy. The most typical indication of its effectiveness is the arrival of your period. You can also take a pregnancy test if your period is late.

There is no other method to determine the effectiveness of Plan B One-Step if signs such as a negative pregnancy test do not occur.

Why Does Plan B Affect Your Period?

Levonorgestrel, the active ingredient in Plan B One-Step, results in possible changes to the menstrual cycle. Levonorgestrel is a synthetic progestin hormone.

It is a lab-made version of a naturally occurring progesterone hormone and acts similarly. 

Because Plan B One-Step contains a more significant amount of hormone than the body naturally produces at various stages of the menstrual cycle, the medication can alter the flow, duration, and timing of the next period.

In general:

• Taking Plan B One-Step after the midpoint of the menstrual cycle (the time of expected ovulation) may result in extended periods and/or delays in period onset.
• Taking Plan B One-Step before the midpoint of the menstrual cycle is more frequently associated with spotting and earlier period onset.

Dosing Guidelines

The table below shows the strength and dosage of Plan B One-Step:

Plan B One-Step can be taken with or without food as long as you take it within 72 hours of unprotected sex. If you vomit within three hours of taking it, you may need to repeat the dose.

Consult a pharmacist or healthcare provider for advice if you have questions about taking Plan B One-Step.

Precautions & Safety

The FDA advises pregnant individuals against using Plan B One-Step. However, the drug is not known to cause harmful effects if taken during pregnancy, and it does not affect an established pregnancy. Plan B One-Step will not terminate an existing pregnancy.

In addition, individuals should not rely on the morning-after pill as their primary form of contraception.

Other options, such as birth control pills or vaginal rings, are more effective when used as prescribed compared to Plan B One-Step or other emergency contraceptive pills.

Certain medications interact with Plan B One-Step and may lead to less effective results for Plan B One-Step when taken simultaneously.

These medications include:

• Some medications that treat HIV, such as Sustiva (efavirenz)
• Certain treatment options for tuberculosis (TB), such as Rifadin (rifampin)
• Medications used to treat epilepsy, such as Dilantin (phenytoin)

Side Effects

Generally, Plan B One-Step provides safe emergency contraception. However, some individuals may experience side effects from the medication.

The most common side effects are:

• Menstrual cycle changes, such as spotting
• Fatigue
• Breast pain
• Nausea
• Headache
• Vomiting
• Abdominal pain
• Dizziness

In most cases, these side effects are mild. Notably, abdominal pain could be a sign of ectopic pregnancy.

If you’re experiencing severe abdominal pain after taking Plan B One-Step, contact a healthcare provider for evaluation and observation.

How Effective Is Plan B One-Step?

Plan B One-Step provides a practical option for preventing pregnancy. In a major clinical study, Plan B One-Step prevented 84% of expected pregnancies.

This was a drop from 8% to 1% in the expected pregnancy rate following unprotected sex without EC.

However, other factors can alter the effectiveness of Plan B One-Step. Studies show that taking the medication as soon as possible after the time of unprotected sex increases the chances of effectively preventing pregnancy.

Furthermore, the point in the menstrual cycle when you take Plan B can affect how it works.

An independent study of Plan B One-Step showed that while the medication may still be effective after ovulation, it is more effective if taken before ovulation.

Summary

Plan B One-Step (levonorgestrel 1.5 mg oral tablet) is an OTC EC pill. It is taken to reduce the chance of pregnancy if taken up to 72 hours after unprotected sex.

After taking Plan B One-Step, it’s common for individuals to experience some changes to their normal menstrual cycle.

Your period can come one week earlier or later than expected. Plan B One-Step may cause spotting and/or periods that are heavier, longer, or lighter than usual.

If more than a week has passed since you expected your period after taking Plan B One-Step, you may be pregnant. Take a pregnancy test; if the result is negative and another week passes without a period, take another test or reach out to a healthcare provider for medical advice.