Taking the morning-after pill can feel like a huge relief after unprotected sex. But sometimes you might wonder if it actually worked.
Plan B and other emergency contraception options are pretty effective when taken quickly. They’re not 100% foolproof.
The most reliable sign that Plan B didn’t work is having a missed period that’s more than seven days late, which should prompt you to take a pregnancy test.
We often get questions about other possible signs that emergency contraception failed. Some people experience symptoms like nausea, increased vaginal discharge, dizziness, or unusual bleeding patterns after taking Plan B One-Step or similar morning-after pills.
While these are common side effects of the medication itself, they don’t necessarily mean the pill failed or worked. Your body can react in all sorts of ways to the high hormone dose in emergency contraception.
If you’re anxious about whether your Plan B worked, keep an eye on your calendar. The timing of your next period might shift a bit because emergency contraception can temporarily mess with your cycle.
But if your period doesn’t show up within a week of when you expected it, that’s your cue to grab a pregnancy test.
How Plan B Works and What to Expect
Emergency contraception can be confusing. We’re here to break it down for you.
Plan B and similar products work in specific ways to prevent pregnancy after unprotected sex. Understanding the basics can help you feel more confident about using them.
Understanding Plan B and Other Emergency Contraceptives
Plan B One-Step (and its generic versions like My Way, Take Action, and Preventeza) is what most folks call the “morning-after pill.” It contains levonorgestrel, a synthetic hormone that’s been around for decades.
These pills are available over-the-counter without a prescription or ID, regardless of age or gender. Another emergency contraceptive option is ella (ulipristal acetate), which requires a prescription but works for up to 5 days after unprotected sex.
It’s actually a bit more effective than Plan B, especially for people with higher body weights. Don’t forget about the copper IUD (intrauterine device)—it’s the most effective emergency contraception out there!
It can be inserted up to 5 days after unprotected sex and provides ongoing birth control for up to 10 years.
How Plan B Prevents Pregnancy
Plan B works primarily by delaying or preventing ovulation—the release of an egg from your ovary. No egg = no chance of pregnancy!
If you’ve already ovulated, Plan B might not work as well. Most people don’t realize that Plan B doesn’t terminate an existing pregnancy.
It can’t affect a fertilized egg that’s already implanted in your uterus. It simply reduces the chance of pregnancy happening in the first place.
After taking Plan B, your body might feel a bit wonky. Some common side effects include:
- Nausea (about 1 in 4 people)
- Irregular bleeding or spotting
- Headaches
- Fatigue
- Breast tenderness
Your next period might arrive earlier or later than expected—typically within a week of your normal time.
Who Should Use Plan B and When
Plan B is for those “oops” moments—when a condom breaks, you miss birth control pills, or you have unprotected intercourse. The sooner you take it, the better!
Its effectiveness drops from 95% when taken within 24 hours to about 61% if you wait 48-72 hours. Weight matters with Plan B.
Studies show it may be less effective for people weighing more than 165 pounds (or with a BMI over 25). If that’s you, talk to your healthcare provider about ella or a copper IUD instead.
Anyone who can become pregnant can use Plan B, regardless of age. It costs around $40-50, but many health clinics offer it at reduced prices.
While it’s a great backup, it shouldn’t replace regular birth control methods. It’s called “emergency” contraception for a reason!
Signs That Plan B Didn’t Work
After taking emergency contraception, it’s natural to wonder if it actually worked. Plan B is about 87% effective when taken correctly, but certain factors can reduce its effectiveness, including timing, body weight, and other medications.
Missed or Irregular Period After Taking Plan B
The most reliable sign that Plan B might not have worked is a missed period. If your period is more than 7 days late after taking Plan B, it’s definitely time to take a pregnancy test.
Plan B can sometimes mess with your menstrual cycle, causing your period to arrive earlier or later than expected. This is totally normal!
But if you’re waiting and waiting and nothing’s happening, that’s when you should be concerned. Some people experience lighter or heavier flow than usual— that’s usually not a problem.
But no period at all? That needs checking.
Unusual Bleeding or Spotting
Spotting after taking Plan B is super common and usually nothing to worry about. However, if you’re experiencing unusually heavy bleeding or spotting that continues for more than a few days, it might be a sign of something else.
Some people mistake implantation bleeding (a sign of pregnancy) for regular spotting after Plan B. Implantation bleeding is typically light pink or brown and happens about 10-14 days after conception.
If you notice spotting but then miss your period, or if the bleeding pattern seems really different from your normal post-Plan B experience, it’s worth taking a pregnancy test just to be sure.
Pregnancy Symptoms After Plan B
Feeling nauseous? Tender breasts?
Unfortunately, these symptoms can be caused by both Plan B AND early pregnancy. Common early pregnancy symptoms to watch for include:
- Persistent nausea or vomiting
- Breast tenderness that doesn’t go away
- Extreme fatigue
- Frequent urination
- Food aversions or cravings
Plan B contains levonorgestrel, a hormone that can cause similar side effects. But typically, Plan B side effects fade within a few days.
If these symptoms persist or intensify after a week, it might be time for a pregnancy test.
Timing and Missed Dose Issues
Plan B works best when taken within 24 hours after unprotected sex. The effectiveness drops to about 61% if taken 48-72 hours later.
If you waited longer than 72 hours, there’s a higher chance it didn’t work. Your body weight can also affect Plan B’s effectiveness.
Research shows it may be less effective for people weighing more than 165 pounds (75 kg). If you’re in this category, chat with your healthcare provider about other emergency contraception options.
Some medications can interfere with Plan B too, including:
- Certain anti-seizure medications
- Some HIV medications
- St. John’s Wort (an herbal supplement)
If you vomited within 2 hours of taking Plan B, the medication might not have been fully absorbed. This is a classic timing issue that reduces effectiveness.
Taking a Pregnancy Test After Plan B
The most reliable way to know if Plan B worked is taking a pregnancy test at the right time. If you’re anxious about whether your emergency contraception did its job, a pregnancy test can give you clarity.
When and How to Use a Pregnancy Test
Wait at least three weeks after taking Plan B before using a pregnancy test. This timeline matters because pregnancy hormones need time to build up in your body.
Testing too early might give you a false negative, even if implantation has occurred. Morning pee is your best friend!
Use your first urine of the day for testing since it contains higher concentrations of pregnancy hormones. Most home tests work similarly—pee on the stick or in a cup and dip the test.
Some can detect pregnancy earlier than others, so check the box for sensitivity levels. Digital tests display clear “pregnant” or “not pregnant” results, while traditional tests show lines that can sometimes be tricky to interpret.
Interpreting Your Pregnancy Test Results
A positive result means you’re likely pregnant, even if the line is faint. Any visible line usually indicates pregnancy.
If Plan B didn’t work, you’ll want to contact a healthcare provider ASAP to discuss your options. Negative results are trickier.
If your period still hasn’t arrived a week after a negative test, test again. About 5-10% of women might get a false negative if they test too early or if the test isn’t sensitive enough.
Your period might be early, late, or different than usual. This is normal.
But if you’re experiencing pregnancy symptoms like nausea, breast tenderness, or unusual fatigue along with a missed period, definitely test again.
What To Do If Plan B Fails
Finding out emergency contraception didn’t work can be stressful. There are clear steps you can take.
Confirming If Contraception Failed
The most reliable way to know if Plan B failed is to take a pregnancy test if your period is late. Don’t panic if you’re just a day or two late—Plan B can sometimes shift your cycle timing a bit.
But if you’re a week late, it’s definitely testing time. Pregnancy tests work best when taken after your missed period, but some sensitive tests can detect pregnancy earlier.
Grab a test from your local pharmacy—no prescription needed. Watch for early pregnancy symptoms like:
- Nausea or morning sickness
- Breast tenderness
- Unusual fatigue
- Light spotting (implantation bleeding)
These symptoms aren’t definitive proof. Confirm with a test and consult a healthcare provider.
Next Steps and Alternative Options
If you confirm pregnancy after Plan B failed, you have several options to consider. First, schedule an appointment with a healthcare provider.
They can confirm the pregnancy with blood tests and discuss your choices without judgment. Your main options include:
- Continuing the pregnancy—Your provider can recommend prenatal care
- Medication abortion—Available up to 10 weeks in many places
- Procedural abortion—Available at different gestational ages
- Emergency contraception alternatives—Like the copper IUD, which can be placed up to 5 days after unprotected sex (and is more effective than Plan B!)
Another emergency contraception option is ella (ulipristal acetate), which works better than Plan B for people weighing over 165 pounds.
Whatever you decide, you deserve compassionate care and support through this process.
Potential Side Effects and When to Seek Help
Taking Plan B can cause some temporary side effects as it contains high hormone levels to prevent pregnancy. Knowing what’s normal and what’s concerning can help you decide if you need medical attention.
Common Side Effects of Plan B
After taking Plan B, you might experience some unpleasant but normal reactions. Nausea is super common—about 1 in 4 people feel queasy after taking it.
If you’re feeling sick to your stomach, try eating something bland like crackers. Spotting or unusual bleeding between periods happens quite a bit too.
This irregular bleeding doesn’t mean the pill failed. It’s just your uterine lining responding to the hormones.
Other typical side effects include:
- Fatigue or dizziness
- Headaches
- Breast tenderness
- Lower abdominal cramping
- Changes to your next period (earlier, later, heavier, or lighter)
Most of these symptoms clear up within 24-48 hours.
Serious Symptoms That Need Medical Attention
While most side effects are harmless, some situations warrant a chat with a healthcare professional.
If you’re vomiting within 2 hours of taking Plan B, the medication might not have been properly absorbed. Give your doctor a ring—you might need another dose.
Severe abdominal pain isn’t normal and could indicate something serious like an ectopic pregnancy. This is a medical emergency, so don’t wait to get help.
Watch out for these red flags:
- Extremely heavy bleeding (soaking through pads/tampons every hour)
- Severe pain in your lower abdomen
- High fever after taking Plan B
- No period within 3 weeks of taking Plan B
If your period is more than a week late, grab a pregnancy test. Plan B is about 87% effective, which means it doesn’t work for everyone every time.