signs that plan B didn't work

What are the signs that plan B didn’t work? Complete guide about Plan B and its side effects, precautions, and other medical information 2023

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Plan B is a pill and it is a form of emergency contraception. This pill contains levonorgestrel. And it is a hormone that is similar to the ones in our body makes. Levonorgestrel can stop sperm from fertilizing an egg. And they cannot be making changes in our cervical fluid and uterine lining as well. So, we can say that Plan B is looking like a round pill and there has one white line on it. Although, these pills are generally very effective. But sometimes it can fail. If we think that our Plan B didn’t work, then we should talk to our doctor about what the next steps might be possible.

There are some options available, and together we can decide on the best course of action for every girl or woman.

Sometimes, we may have had unprotected sex around the time that our ovulation occurred, and it is about 5 to 7 days before the day of our expected period starts.

If sperm are in our reproductive tract when we ovulate. They can fertilize an egg even if it has been there for only a short time only. If we take Plan B, after we ovulate, then it may not be effective in preventing pregnancy.

If any of us are worried about unintended pregnancy, then we are probably not alone. When any woman is taking Plan B then she may be able to prevent an unplanned or unwanted pregnancy. Though it’s not 100% effective.

If one of us took signs that plan B didn’t work and we’re wondering if it worked, we’re in the right place. Below, we outline how to know if Plan B has failed and also get review some factors that can influence its efficacy. 

In this article, we will discuss all the comprehensive detail of these emergency contraception pills. We will also discuss and describe symptoms, benefits, risks, and every possible information with you. So, let’s get started from here:

What do you know about and signs that plan B didn’t work?

As is nicknamed the “morning-after pill. And Plan B is it’s a brand of emergency contraception. We can take it within five days of having unprotected sex. We can purchase Plan B over-the-counter without a prescription.

Moreover, Plan B works by delivering our body a strong dose of levonorgestrel. It is a synthetic form of progesterone. By administering or using 1.5 milligrams of levonorgestrel, then this Plan B may prevent pregnancy by delaying ovulation time in the body. 

Ovulation and mature eggs—- signs that plan B didn’t work:

Ovulation occurs when a mature egg is released from our ovary into our fallopian tube. This egg waits there for 12 to 24 hours to be fertilized by male sperm. If they are not fertilized within this time frame, then they will disintegrate. By delaying ovulation, it can keep any sperm in our body from fertilizing our egg after unprotected sex. 

This pill works by preventing pregnancy. But, it can’t end an existing pregnancy. It won’t work if there is a fertilized egg and it has already been successfully implanted in our uterus. 

How to take these pills:

signs that plan B didn't work

As we all know, Plan B should be taken as soon as possible after having unprotected sex. Hence why it is referred to as an emergency contraceptive method. But we did not know how long Plan B stay in our system. And when is Plan B most effective? Plan B is most effective when we take it within 72 hours. Though, this pill may still work for up to five days.

Once we take Plan B, then we may experience some side effects, such as:

Menstrual irregularity 


Abdominal cramping

Breast tenderness






How do we know that our signs that plan B didn’t work?

Research and medical study show that Plan B can be up to 89% effective. It is depending on when we take it. However, there’s always a chance that we may still get pregnant.

Here are a few signs that plan B didn’t work properly:

Missed period:

It is the most important and dangerous sign is missed period or missed monthly cycle. And importantly, it is a tell-tale sign that Plan B didn’t work. It is if we don’t get our period within four weeks of taking the medication. While it may cause our period to come earlier or later than expected date. It missing it altogether may indicate that we’re getting pregnant. 


It is also a common side effect of this emergency contraceptive pill, but we can also experience spotting from implantation. However, implantation bleeding usually takes place within 10 to 14 days after ovulation. In other words, pill spotting typically sets in within a few hours or days of taking the medication. It is the most common sign of pregnancy.


signs that plan B didn't work

In other contrast, Plan B can cause fatigue or vomiting. It also persists and usually only lasts a few days. It is also known as Pregnancy fatigue.

Fatigue can persist through all three trimesters during pregnancy. Even the earliest stages of pregnancy can zap our energy. 

Food cravings and aversions:

Pregnancy can notably alter our food preferences. We may find ourselves with self-cravings for new foods or being put off by some of our favorite staples. We may also lose our appetite altogether. Our Food preferences can change and also set in within a few weeks of getting pregnant.

Heightened smell sensitivity:

There is one of the most important reasons is increased sensitivity. And that is why pregnancy can cause food aversions. It is also caused the heightened sensitivity to smell. Many Women and people who menstruate often have much stronger responses to scents and fragrances while they are getting pregnant.

Morning sickness:

If we find ourselves feeling nauseous or vomiting for no reason, then we may be pregnant. Unlike the name suggests, it is also known as morning sickness. These signs can occur at any point in the day. We must keep in mind that short-term nausea and vomiting are also side effects of signs that plan B didn’t work with contraceptive pills.

Light-headedness and headaches:

 While plan B can cause some kind of dizziness, so it can the early stages of pregnancy. During pregnancy, our blood vessels dilate roughly 50% to funnel more blood flow to our developing fetus. Our blood pressure can drop, and it is leading to dizziness, lightheadedness, and headaches.

Needing to pee more often:

 While pregnant, your kidneys go into overdrive to filter your increased blood flow. As a result, you may find yourself taking more frequent trips to the bathroom. Increased urination typically begins right before your missed period.

Breast tenderness or swelling in signs that plan B didn’t work:

 As our hormones shift during pregnancy, then our breasts may become sore, swollen, and tender. And our nipples and areolas may also darken and become enlarged. So, breast tenderness is also a plan B pill’s side effect. But nipple and areola changes are not.

Abdominal cramping:

During pregnancy, there is more blood flows to the uterus, and it can induce cramping and abdominal discomfort. However, cramping is also a very common symptom of PMS and a side effect of plan B.

Mood swings:

As pregnancy alters our hormones, we may find ourselves feeling more moody, irritable, sad, or anxious. We may also experience sudden mood fluctuations and also changes. That’s because pregnancy hormones can affect all our brain’s neurotransmitters.

As we can see, cramping, food cravings, or bleeding after plan B ingestion, are many of the early signs of pregnancy. It also resembles Plan B’s side effects. Thus, the only way to find out if we are pregnant is to take a pregnancy test.

What makes plan B so ineffective? signs that plan B didn’t work

signs that plan B didn't work

As we mentioned before in this article, it is not 100% effective. So, what influences its efficacy rate? 

Here are some factors that may affect how good plan B works for us:

How quickly do we take pills and signs that plan B didn’t work?

 – Plan B’s efficacy wanes as time goes on. If you take Plan B within three days, its efficacy rate can be as high as 75% to 89%. If we take it within four to five days, that rate may be lower. 

Menstrual cycle phase: signs that plan B didn’t work

 Where we are within our menstrual cycle can also play a vital role in how well this works. If we have unprotected sex while we’re ovulating or right after, then it may not work, since it won’t be able to delay any ovulation phase

Weight problem:

 It is less effective for most of the females who have BMIs of 30 or higher. If our BMI is between 30 and 35, then we may want to take Ella instead. As we all know, it’s a prescription form of emergency contraction. It may be more effective for people with higher BMIs.

Patient’s medications:

There are certain medications and herbal supplements that can interfere with it and they are including:


Some seizure medications

Some HIV medications

Certain antibiotics and antifungal medications

St. John’s wort herbal supplements

If we are taking any of these drugs, then we should make sure to consult with our doctor before taking them or any other emergency contraceptives. 


If we throw up within two hours of taking them, we may expel some of the medication in the process, leaving us unprotected.


Timing is the main hero of all this procedure. It is also important to note that these pills won’t prevent pregnancy during sexual encounters that occur after we take them. If we plan to have sex after taking them, then we make sure to use another form of protection.

What are the most frequent chances of pregnancy and what are the signs that plan B didn’t work?

signs that plan B didn't work

Even if this pill fails, we won’t necessarily get pregnant from one unprotected sexual encounter. It’s always possible, but it depends greatly on where we are in our menstrual cycle.   

Study shows that there is a high chance of a young, healthy couple getting pregnant from one instance of unprotected sex around one in 20. 

Our odds of getting pregnant will depend on our health:

Menstrual cycle phase



Why doesn’t plan B work during ovulation? And what are the signs that plan B didn’t work?

As we discussed earlier, it is the primary method of preventing any pregnancy. It is delaying ovulation. If we’ve already ovulated, there’s not much more, that it can do. 

Ovulation itself only lasts 12 to 14 hours, though we can still get pregnant for a few days before and after ovulation time.

Is there anything that we can do during ovulation to prevent pregnancy? Signs that plan B didn’t work:

This pill is not our only safeguard against pregnancy. It’s also not meant to be used as a regular birth control pill or method. So can we take Plan B on birth control? The short answer is, yes. It is the best method and is used as a backup method when our primary birth control method doesn’t go as planned. 

Here are a few pregnancy control methods that can work during any time of the month, including ovulation:


Birth control pills

Copper or hormonal IUDs


Contraceptive sponges

Hormonal injections

Vaginal rings

Skin patches


Vaginal gel

Tubal ligation

Do these contraceptive pills work during ovulation? Signs that plan B didn’t work

signs that plan B didn't work

These are morning-after pills and they are the most effective method before ovulation. It is because they may stop an egg from being released from the ovary so there is no egg available to get fertilized by sperm. But if we’ve already ovulated, then this pill may prevent sperm from fertilizing an egg as well.

If there is enough time and it has passed after unprotected sex and an egg has already been fertilized, then they may stop the egg from implanting in the uterus. But if the fertilized egg has already been implanted in the womb before taking them. Then it’s most unfortunately too late, and it won’t prevent pregnancy. Timing is the key hero here.

signs that plan B didn’t work and protected sex:

After having sex, this can take up to six days for an egg to get fertilized. And there is required another three to four days for the fertilized egg to implant itself into the uterine lining. If we’re within our fertile window, then using the copper IUD as emergency contraception is a safer option to avoid pregnancy.

It may also be helpful to know that if we take a morning-after pill and we are already pregnant, it won’t harm the fetus as well. So, don’t worry about using it.

As we can see, it may be able to reduce our chances of getting pregnant after unprotected sex. If we need emergency contraception or a new birth control prescription, then this guide has covered all your concerns. 

How long will the side effects of plan B last?

The side effects like headaches and nausea would fade within a few days. If any patient’s next period might be delayed by up to a week, or it might be heavier than usual. Then she should consult his health doctor first. Moreover, these changes should only affect the period right after we take the plan B pill.

If we don’t get our period within a week of when it was expected, then we should take a pregnancy test.

Most Frequently Asked Questions about signs that plan B didn’t work (FAQs)

1: Is there any bleeding symptoms after I take plan B?

Ans: We might experience light bleeding and it is called spotting. After taking this pill. Even though this doesn’t happen to every lady who takes this pill. And we should not worry about using of these plan B. If we notice that the bleeding is heavier or happens after we’ve missed a period, reach out to our healthcare provider. So, we can say that spotting happens after a missed period and it could be implantation bleeding. 

2: Can a morning-after pill make our period late or disrupt our cycle?

Ans: The morning-after pill can cause our next period to be irregular. If our period is late or abnormal, contact our healthcare provider and we should consider taking a home pregnancy test. Our provider will advise us on our next steps if our menstrual cycle doesn’t return to normal.

3: What are the side effects of signs that plan B didn’t work?

Ans: There are some short-term side effects are following here:






Lower abdominal pain or cramps

Tender breasts

Spotting between periods

Irregular or heavy menstruation

4: What is the cost of signs that plan B didn’t work?

Ans: One dose of plan B or its generic forms generally costs between $25 and $60.

5: What are the three types of emergency contraception pills?

Ans: There are three types of emergency contraception (EC) or “morning after” pills available in this market.

levonorgestrel (Plan B) or it can also be called a progestin-only pill. The second number of pills is ulipristal acetate (Ella), a pill that’s a selective progesterone receptor modulator, meaning that it blocks progesterone. And the third number of pills are estrogen-progestin pills (birth control pills).

The Final Words:

Signs that plan B didn’t work are not a big problem. We shouldn’t attempt to use morning-after pills or any type of Emergency Contraception as our regular birth control. We should speak to a healthcare professional about a more effective and longer-lasting method, like the pill, patch, or other shot.

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