Worried because your period is late after taking Plan B? You’re not alone—and you’re not necessarily pregnant either. Many people often ask, ‘Can Plan B cause your period to be late?’
Plan B (also called the morning-after pill) is a powerful emergency contraceptive, but it can impact your menstrual cycle in surprising ways. This article explains how and why it can delay your period, what to expect, when to test for pregnancy, and when to consult a doctor.
Can Plan B Make Your Period Late?
Yes, Plan B can make your period late.
It contains a high dose of the hormone levonorgestrel, which delays ovulation and shifts your cycle. As a result, your next period might arrive a few days early, a week late, or feel heavier/lighter than usual. These effects are temporary.
How Plan B Delays Your Period: The Hormonal Reason
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It happens because Plan B contains a high dose of the hormone called levonorgestrel, which delays ovulation (the release of a mature egg from an ovary) to prevent pregnancy.
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This, in turn, leads to hormonal disruption, which contributes to a late or delayed period than usual.
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In addition, changes in the menstrual cycle can lead to early periods, spotting between periods, and heavier or lighter bleeding than normal.
Other Factors That Might Impact Your Period
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Apart from Plan B, factors such as illness, stress, dietary changes, and underlying health issues can also cause a delay in your period.
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A later period does not always mean pregnancy or other severe problems, but it is crucial to stay alert to any unusual changes in your menstrual cycle.
How Long Can Plan B Delay Your Period?
The hormones present in Plan B can delay periods in several ways. While some women notice no change, other reports the fluctuations in timing and duration of the next period:
Timing
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Some women get their period within the usual time as expected, while others may experience it a couple of days earlier or 1 week later than the normal timing.
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It is found that the earlier you take the morning-after pill in your menstrual cycle, the earlier the next period will come. However, it has not been proven clearly yet.
Duration
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The duration of the period might also change, but there is a chance that it might last for a similar length of time as normal.
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A study reports that taking emergency contraception (e.g., Plan B) later in the menstrual cycle (2 or more days after ovulation) can make the period last longer than usual.
What to Expect After Taking Plan B: A Simple Timeline
| Days After Taking Plan B | What Might Happen |
|---|---|
| Day 1–3 | Possible spotting or mild symptoms |
| 1–7 days before expected period | Period may arrive earlier |
| 1–7 days after expected period | Period may be delayed (common) |
| 14+ days late | Take a pregnancy test |
How Will Your First Period Be After Taking the Morning-after Pill?
Your first period after using Plan B pills may be completely normal and on time, or it might come with these types of irregular bleeding:
It is believed that most changes in the menstrual cycle disappear after the first period post-taking the Plan B dose. However, if the problem lasts longer, seek medical attention.
Why Plan B Affects Your Menstrual Cycle
This happens because:
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Plan B contains a higher amount of levonorgestrel, a synthetic hormone, which stops pregnancy by preventing the ovary from releasing a mature egg.
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This extra amount of levonorgestrel impacts the menstrual cycle, which leads to earlier and delayed periods and also heavier or lighter bleeding.
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These changes can affect your period, making it come earlier or later, and the bleeding might be heavier or lighter than usual.
When to Worry About a Late Period After Plan B
It is normal for Plan B to impact your period timing. However, if your period is 2 or more weeks late, the best suggestion is:
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Take a pregnancy test: The best idea is to take a pregnancy test, as pregnancy can be a possibility.
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Monitor your symptoms: Keep a track of symptoms such as heavy bleeding or severe abdominal pain, as they can indicate some other underlying issues.
If test results are negative, wait for a few more weeks to allow your periods to come. If it doesn’t arrive, take a pregnancy test again. In case the test comes negative once again, consult your gynecologist/obstetrician for proper advice.
When Should You Take a Pregnancy Test After Plan B?
Delayed periods can be very stressful for women. So, the right time to take a pregnancy test is if:
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You have taken Plan B, and 7 days have passed since you expect your period to start.
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It has been three weeks since you took the pill, and the period has still not arrived.
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It’s been 21 days since you have had sex without protection
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You had engaged in unprotected sex after using Plan B and did not take it again.
If you have any other concerns or questions, seek medical guidance. This can help prevent the risk of any issues or complications.
Other Side Effects of Plan B You Might Notice
In general, the Plan B or morning-after pill is a safe emergency contraceptive method. However, along with a delayed period than usual, research reports the following side effects of Plan B in some women:
These side effects are mild and usually last for a short period when you use Plan B. Mostly, they subside in 1 or 2 days. However, severe abdominal pain could indicate ectopic pregnancy (a pregnancy marked by implantation and growth of an egg outside the uterus). In such a case, see a doctor for proper evaluation.
Precautions and Safety While Taking Plan B
Follow these precautions and safety tips when using it:
- Do not depend on Plan B as the primary way to prevent conception.
- Certain medicines may interact with Plan B, which can reduce its effectiveness. Those medications include:
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Certain HIV medicines, like Sustiva (efavirenz)
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Some medications to treat tuberculosis, such as Rifadin (rifampin)
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Medicines for epilepsy, like Dilantin (phenytoin)
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Certain anti-seizure medicines, such as Carbamazepine, Phenytoin, or Rufinamide
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Supplements, like St. John’s Wort
So, always inform about your medications to your doctor, who can help find whether Plan B is suitable for you.
Final Thoughts: Don’t Panic—Stay Informed
It’s totally valid to ask, “Can Plan B make your period late?” for a woman if she has recently taken it. The answer is yes, but it’s usually temporary and nothing to worry about. Your body just needs a little time to adjust after the hormone shift.
If your period is over 2 weeks late or you have concerning symptoms, take a pregnancy test and speak to a healthcare provider for peace of mind.
Related Read: Can Being Sick Delay Your Period? Here’s the Truth
Frequently Asked Questions
Is it normal to bleed after taking Plan B?
Yes, it is normal and occurs when the high dose of progestin in Plan B changes the menstrual cycle, leading to irregular bleeding. The bleeding happens within a few days of taking Plan B or sometimes some weeks later.
What are the signs that the Plan B pill didn’t work?
If you miss your period, this is a sign that your Plan B pill has not shown any effects. In case your period is 7 or more weeks later, take a pregnancy test and consult a doctor.
Will Plan B affect future fertility?
Though Plan B prevents ovulation for a temporary period, it does not cause long-term impact on the ability of women to conceive.
Can the morning-after pill delay your period for 2 months?
No, there is no possibility. But it can cause a delay in the period for only a couple of days or one week. If there is a significant delay, especially over 3 weeks, take a pregnancy test and consult a gynecologist.
What does Plan B not do?
It doesn’t end an existing pregnancy and does not protect against STIs or sexually transmitted infections.
