Does plan b give you pregnancy symptoms

• Emergency contraceptives, like Plan B One-Step, use a synthetic hormone called levonorgestrel, which mimics the sex hormone progesterone, which prevents ovulation and, hence, pregnancy.
• Plan B contains three times more levonorgestrel than a regular birth control pill. As a result, this large, concentrated dose can cause side effects like fatigue, nausea, and pelvic pain.
• Side effects of taking Plan B shouldn't last more than a few days. If they feel severe or worsen after a few days, you should speak to a doctor.
• You can't prevent Plan B side effects entirely, but you may be able to manage your symptoms with anti-nausea medicine or a pain reliever to reduce discomfort.
• This article was reviewed by Julia Simon, MD, who is an assistant professor with the Department of Obstetrics and Gynecology at UChicago Medicine.
• Visit Insider's homepage for more stories.

Plan B is an over-the-counter emergency contraceptive that should be taken within 72 hours of unprotected intercourse to prevent pregnancy. Emergency contraceptives come in many brands including Plan B One-Step, Aftera, Econtra EZ, Take Action, Preventeza, and more.   

Here's what to expect if you take a Plan B pill.

The Side Effects of Plan B

The way emergency contraceptives work is that they contain a large dose of levonorgestrel. Levonorgestrel is a synthetic hormone that mimics the sex hormone progesterone, which prevents ovulation and, hence, pregnancy.  

Plan B and other emergency contraceptives contain 1.5 milligrams of levonorgestrel. That's three times more than what you get in a regular birth control pill. As a result, this large, concentrated dose can cause side effects like:

• Fatigue
• Nausea
• Pelvic pain

Less common side effects include:

• Vomiting
• Headaches
• Breast tenderness

You might also notice changes to your menstrual cycle, like irregular bleeding.

While Plan B side effects can be uncomfortable, they shouldn't feel excessively extreme or severe. If your side effects continue or become worse after more than a few days, visit with a doctor. 

How long Plan B side effects should last

"The duration of side effects is variable from woman to woman," says Dr. Nina Carroll, MD and OB-GYN of Your Doctors Online. But here is what the experience could look like if you decide to use Plan B.

• Day 1: After taking the pill, you may experience mild side effects like nausea, vomiting, and pelvic pain. Some people may vomit within two hours of taking the pill. In this case, it is important to retake the pill to guarantee its effectiveness.
• Days 2 and 3: Symptoms may continue over the course of days two and three. 
• Day 4: Most people will no longer experience the side effects of taking a Plan B after four days of using the pill. 
• Days or weeks later: Menstrual changes are a common experience for its users and the symptoms may not show up until a woman's next menstrual cycle, which may be anywhere from days or even weeks after taking the pill.

How to relieve Plan B side effects

Unfortunately, there's nothing you can do to make the side effects resolve more quickly or prevent them from happening in the first place. 

However, you may be able to manage your symptoms. Doctors may suggest an anti-nausea medicine or pain reliever to reduce discomfort.

Related stories about contraception:

• The first clinical trial of a male contraceptive gel is starting in the UK, and it could mean an alternative to the pill
• Male contraception hasn't changed much since the condom was invented over 5,000 years ago. You can blame biology.
• A startup seeded by Silicon Valley's hottest mentorship program aims to bring the first male birth control to market
• Getting pregnant while taking contraception could be beyond your control if you have a certain gene

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