Drugs Q & A

What Are The Signs That Plan B Didn’t Work Properly?

Studies have shown that although most unintended pregnancies occur because couples do not use contraception, contraceptive failure is also a major underlying cause, particularly where contraceptive prevalence is high and where the contraceptive method mix skews toward methods with higher failure rates.

The global rate of unintended pregnancy is estimated at 44% of all pregnancies, corresponding to approximately 62 unintended pregnancies per 1000 women between the ages of 15–44 years old.

What is Plan B?

Plan B is an emergency contraceptive pill for women, it contains 1.5 mg of levonorgestrel—an ingredient that is also commonly found in birth control pills. Plan B can prevent pregnancy when people have sex without contraception. Plan B does not end an already established pregnancy and does not protect against sexually transmitted infections (STIs).

How does Plan B work?

If taken within 72 hours of unprotected sex or following a contraceptive accident, Plan B works by:

  • Stopping ovulation temporarily
  • Preventing fertilization
  • Preventing implantation

Unlike regular birth control methods, which are used before or during sex, Plan B is used to prevent pregnancy after unprotected sex or following a contraceptive accident.

If taken within 3 days (72 hours) of unprotected sex, Plan B can reduce the chance of pregnancy by 75 to 89 percent. According to Plan B’s manufacturer, the sooner you take the pill, the more effective it is.

Research has found that Plan B is “moderately effective” when taken between 72 and 120 hours after sex. But remember that its effectiveness decreases the longer you wait.

How do I use Plan B morning-after pills?

Take Plan B morning-after pills as soon as you can after unprotected sex. Simply swallow the tablet the way you would any other pill. Read the instructions that come in the package for more information.

You can take Plan B up to five days after unprotected sex, but they work much better if you take them during the first three days.

Take a pregnancy test if you haven’t gotten your period within three weeks after taking the morning-after pill.

Take Plan B One-Step morning-after pill if:

•     You didn’t use any birth control.

•     The condom came off or broke.

•     The diaphragm slipped out of place.

•     You missed at least two or three active birth control pills in a row.

•     You forgot to insert your ring or apply your patch.

•     Your partner didn’t pull out in time.

•     You have another reason to think your birth control might not have worked.

•     You were forced to have unprotected sex.

Remember: Plan B will not protect you from getting pregnant if you have unprotected sex after taking it. To protect you against getting pregnant, you need to take it right after you have unprotected sex and use a form of contraception when you have sex.

Do not take Plan B if:

•     You know you are pregnant or suspect you might be.

•     You have a history of allergy or hypersensitivity to its ingredients.

•     You have a history of recent abnormal vaginal bleeding that your doctor has not yet evaluated.

signs that plan b didn't work properly

What are the signs that Plan B didn’t work?

Getting information on how to know if plan b worked before your period can prevent anxiety as no contraceptive including Plan B is 100% reliable. Birth control pills like Plan B are 99 percent effective with “perfect use but can also fail to work properly.

Plan B is designed to maintain a constant level of hormones in your body temporarily. If you did not take it at the right time, your hormone levels can drop quickly. Depending on where you are in your cycle, this may cause you to ovulate. Ovulation can increase your chances of becoming pregnant.

Reckless alcohol consumption can also cause Plan B failure. While under the influence, some women may forget to take the pill at the correct time. If you vomit too soon after taking Plan B, your body may not be able to absorb any of the hormones. This can result in a drop in your hormone levels, which could trigger ovulation and result in Plan B failure.

Many people go online looking for signs that Plan B didn’t work on Reddit, while others go in search of Plan B symptoms 2 weeks later.

The internet is replete with many Plan B didn’t work stories as well as pregnant after Plan B stories. However, pregnant after morning-after pill symptoms are the best signs that Plan B might have failed to work as expected.

The following are some of the signs that Plan B didn’t work:

Light Headedness

If Plan B didn’t work, you might feel dizzy or light-headed at times indicating that you might be pregnant. After you get pregnant, your blood vessels dilate to prepare for the increased blood flow, which lowers blood pressure and creates that feeling of lightheadedness.


Another sign that Plan B did not work correctly is fatigue which is one of the most common early signs of pregnancy. Activities that never phased you before may tire you out, and you might want to sleep a lot even if you have gotten 7-9 hours already. The body is producing more blood to support the developing baby, which can cause fatigue and increase your need for nutrients. These symptoms usually last through the first trimester and can be alleviated by resting, eating a nutrient-rich diet, and drinking plenty of fluids.

Breast Changes

If Plan B did not work as it should, you may notice your breasts may become heavy, swollen, or tender. Some women experience this symptom before their period, so it can be confused with PMS. However, one thing that happens during the early weeks of pregnancy that does not occur during a regular menstrual cycle might tip you off. If your areolas – the circles of pigmented skin surrounding the nipples – may darken or even become enlarged.


Some women experience spotting as an early sign of pregnancy. Small amounts of light pink or brownish blood may appear a week or so before your period is due which implies that your Plan B pill did not work as it should. This type of spotting is called implantation bleeding. As the fertilized egg attaches to the uterine lining, it can cause irritation and light bleeding. Sometimes this is mistaken as a period, but spotting is usually much lighter than a regular period.


Another sign that Plan B didn’t work that can be confused with PMS or a regular period is cramping. During pregnancy, blood flow increases all over the body. Increased blood flow in the uterus can cause cramping. These cramps are usually mild, but if they become severe enough to affect your daily routine, you should see your doctor. Many women experience similar cramping right before their regular menstrual period, but it’s a common early symptom of pregnancy. So, if you have cramps (or the spotting mentioned above), don’t give up hope that you’re pregnant just yet.

Changes in Food Preference

If you suddenly discover that your food preference has changed, it is likely that Plan B did not work and you are pregnant. Strange food cravings are a staple cliche in TV and films about pregnant women. However, that stereotype is rooted in reality. Many pregnant women develop cravings or aversions to food a few weeks after conception. You might find yourself wanting to eat things you don’t usually eat. Your favorite foods might suddenly make you nauseous. Or you may lose your appetite altogether.

Sensitivity to Smells

For some women, contraceptive failure and the resulting pregnancy makes their sense of smell go into overdrive. Exaggerated reactions to certain smells can tie into morning sickness and food preference. Scents that are not very strong to other people can be pungent and unpleasant to a pregnant woman.

Frequent Urination

If Plan B didn’t work, it implies that fertilization has taken place. After conception, your kidneys start working harder to filter the increased blood flow, resulting in the urge to urinate more frequently. This symptom can start right before your missed period.

Morning Sickness

Morning sickness is notoriously incorrectly named. As most pregnant women can tell you, it can happen at any time. It is also a common early sign of pregnancy before you miss your period. A few weeks after conception, your body produces more estrogen and progesterone, causing nausea or vomiting. According to the American College of Obstetricians and Gynecologists (ACOG), morning sickness subsides after the first trimester for some women, while others have it throughout the entire pregnancy.

Can Plan B cause birth defects if taken during early pregnancy?

While some research has suggested a link between the use of birth control pills near conception and an increased risk of low birth weight, preterm birth, or congenital urinary tract abnormalities, these concerns generally haven’t been observed in clinical experience.

As a precaution, if you suspect you’re pregnant, take a home pregnancy test. If the home pregnancy test is positive, stop taking the pill. If taking a home pregnancy test isn’t possible, stop taking the Plan B until the pregnancy is confirmed or ruled out. In the meantime, use another method of birth control — such as condoms.

If you’re concerned because you took Plan B before you knew you were pregnant, talk to your health care provider, but be assured that there’s little risk.

What are the side effects of Plan B morning-after pill?

Plan B One-Step can cause side effects for some people. According to the FDA, some reported side effects include:

•        breast tenderness

•        dizziness

•        fatigue

•        headache

•        late period

•        lower abdominal pain

•        menstrual bleeding that is heavier than usual

•        nausea

The most common side effect of Plan B One-Step is heavier menstrual bleeding. Otherwise, the FDA generally regards the medication as safe. In addition, People who are breastfeeding, or chestfeeding, can use the medication without adverse effects.

What Drugs can affect the effectiveness of Plan B?

Certain medications can alter the effectiveness of Plan B.

If you take any of the following, speak with a healthcare professional before buying Plan B:

•        rifampin (an antibiotic)

•        griseofulvin (an antifungal)

•        St. John’s wort (an herb)

•        seizure medications, including carbamazepine, phenobarbital, and primidone

•        some HIV medications, including efavirenz

Although the manufacturers advise taking Plan B within 3 days of unprotected sex, you can take it up to 5 days after penis-in-vagina sex.

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