Unexpected Reasons Plan B Might Not Work

Life is full of unexpected moments, especially when it comes to sexual encounters. Things can happen like forgetting to take your birth control pill or having a condom break. This is why emergency contraception like Plan B is a good alternative. However, it's essential to understand there are times when Plan B might fail, even when you've followed every direction. Several different reasons can factor into your emergency contraception unexpectedly not working properly.

Plan B is an emergency contraception made up of the drug levonorgestrel. It works by suppressing ovulation so the sperm cannot fertilize an egg. According to the manufacturer, this form of contraception must be taken within 72 hours of the sexual encounter. It's also sold over the counter; and, like other forms of birth control, it doesn't hinder your chances of getting pregnant in the future.

You don't want to worry about your birth control not working in an emergency. Let us help you explore a few unexpected reasons why Plan B might not work for your situation.

You've already ovulated

You might have heard that pregnancy is all about timing. Plan B is no different. According to the U.S. Food & Drug Administration (FDA), this drug works by delaying the release of the egg. So, it must be taken before ovulation to stop the egg from reaching the ovary. Healthline points out that since the egg has already left the ovary during ovulation, Plan B will be much less effective. In fact, a study in Contraception notes that Plan B was only 68% effective when used during the fertile days.

Ovulating, like PMS, gives you a few signs that it's coming. The first is your temperature, according to WebMD. During ovulation, your resting or basal temperature can fall and rise again. You'll also notice thinner cervical mucus, tender breasts, bloating, and cramps. It can also be helpful to watch your calendar since ovulation typically occurs about 12-14 days before the start of your next period, states Johns Hopkins Medicine. Since emergency contraception doesn't work during ovulation, using a consistent form of birth control is recommended during this time.

You have a higher BMI

You might not consider your body weight regarding medication beyond getting the correct dosage. However, your body weight might factor in Plan B's effectiveness. A study published in Contraception in 2015 showed a significant drop in the efficacy of Plan B with a higher body mass index (BMI). Therefore, those with a BMI of over 26 might find this medication less effective than other emergency contraceptive medications. The study also noted that those with a higher body weight might experience the same risk as the wait-and-see method.

OB-GYN Dr. Allison Edelman told the OHSU Center for Women's Health, "The study showed that levonorgestrel is the most likely of the options to fail for women with a higher BMI."  The mechanisms behind this aren't entirely understood, but Dr. Edelman is looking into the dosage. She did a study on doubling the dose for those with higher body mass index with some success. However, the study was very small. She also noted, "Doubling the dose doesn't necessarily mean that your body will see double the dose. Drugs go through our system along a variety of pathways and we metabolize different drugs in different ways, so it's usually not that simple."

You're taking other drugs that interact with Plan B

Before you run out and buy Plan B to prevent pregnancy, look at the medications you already have in your cabinet. It can be worthwhile to certain individuals since the efficacy of Plan B can be affected by specific drug interactions. For example, those who take clobazam for seizure disorders might find that Plan B doesn't work to stop ovulation and pregnancy, even if you follow all the directions to the T. According to StatPearls, anticoagulants, antidiabetic medications, barbiturates, antibiotics, and St. John's wort can diminish the drug's effectiveness. It also listed the drugs rifampicin, rifabutin, and griseofulvin.

Since Plan B isn't the only form of emergency contraception, you can talk with your doctor to try other brands that might work with the medications you are taking. Sometimes, your healthcare provider might also note that Plan B is beneficial even with the reduced effectiveness.

Additionally, you can take Plan B while taking birth control pills. Medical News Today notes that Plan B and birth control bills can be used in conjunction after unprotected sex. But it can affect your cycle, making your period earlier or later and heavier than usual.

You had unprotected sex after taking it

Plan B is called the morning-after pill for a reason. For it to be effective, you need to take it the morning after having unprotected sex. But, unlike a birth control pill or intrauterine device, it won't protect you from any unprotected sex a day or two after taking it. The pill is only effective if you take it right after your encounter. WebMD notes that it's essential to take the pill within 72 hours after having unprotected sex. It's simply emergency contraception that doesn't have any long-standing effect.

WebMD also notes that the closer you take it after having intercourse, the more effective it is. For example, it's about 87% effective when you take it within 72 hours. But it can be even more effective if it's taken within 24 hours. For additional encounters, additional pills may be needed. So, if you have additional sexual encounters, you need to take Plan B each time within 72 hours for it to work.

Medical News Today states that there isn't a limit on how many times an individual can take Plan B. Using it as a regular form of birth control is not recommended, however, because it's not as effective as other methods.

You vomited after taking it

Like most medications on the market, Plan B has a few potential side effects that are important to be aware of, including nausea and vomiting. This can be a bummer since the medication needs to be dissolved in the stomach to be absorbed in the blood to be effective. Therefore, if you vomit one to two hours after taking the pill, it might not work, according to WebMD. Since Insider lists nausea and fatigue as the most common side effects, it's very possible that the pill could cause you to vomit.

The American Academy of Allergy, Asthma & Immunology also notes that vomiting after taking a medication can indicate an allergic reaction, especially when it's coupled with rashes and a cough. So, if Plan B makes you sick, you might want to consult a health specialist before trying it again.

Plan B is an effective emergency contraception method, but there are certain cases where it might not work as effectively as it should or even at all. It's vital to discuss any risk factors you might have with a healthcare provider before using it.