Drinking alcohol after taking Plan B is not dangerous and won’t stop the pill from working. There is no major drug interaction between levonorgestrel (the active ingredient in Plan B) and alcohol. The main concern is practical: alcohol can make Plan B’s already-unpleasant side effects feel worse, and heavy drinking could lead to vomiting that actually does compromise the pill’s effectiveness.
Why Alcohol Won’t Reduce Plan B’s Effectiveness
The interaction between alcohol and levonorgestrel is classified as “minor” in clinical databases. There’s no evidence that drinking interferes with how Plan B prevents pregnancy. The pill works by delaying ovulation, and alcohol doesn’t change that mechanism.
That said, the data on how these two substances interact in the body is limited. Oral contraceptives may slightly slow alcohol metabolism through enzyme inhibition, meaning your body could process drinks a bit more slowly than usual. The effect is unpredictable and not well studied, but it’s worth knowing you might feel alcohol’s effects more than you’d expect.
The Real Risk: Vomiting
This is the one scenario where drinking after Plan B can actually matter. If you vomit within three hours of taking the pill, your body may not have absorbed enough of the medication for it to work. In that case, you’d need to contact a healthcare provider about whether to take another dose.
Alcohol on its own can cause nausea and vomiting. Plan B on its own commonly causes nausea and vomiting. Combining the two raises the odds that you’ll throw up during that critical three-hour absorption window. If you took Plan B recently, even moderate drinking creates a real risk of undermining the whole point of taking it.
Overlapping Side Effects
Plan B frequently causes tiredness, nausea, headaches, dizziness, and sometimes vomiting. These are also common effects of drinking. When you combine the two, these symptoms can stack. A headache that would have been mild becomes pounding. Mild queasiness becomes full-blown nausea. Dizziness that you could have ignored becomes enough to knock you off your feet.
None of this is medically dangerous, but it can make for a miserable experience. If you’re already feeling side effects from Plan B, adding alcohol will likely amplify them.
How Long to Wait
If you want to be cautious, waiting at least three hours after taking Plan B before having any drinks gives the pill enough time to be fully absorbed. At that point, vomiting is no longer a threat to the medication’s effectiveness. If you’re already experiencing nausea from the pill, it’s worth waiting until that passes before drinking, since alcohol will only make it worse.
If you’ve already had a few drinks and need to take Plan B, don’t delay. Timing matters far more than whether there’s alcohol in your system. Plan B is 81 to 90 percent effective at preventing pregnancy, and that number depends heavily on how quickly you take it. It works best within 72 hours of unprotected sex and becomes less effective after that, with some reduced benefit up to 120 hours. Waiting until you’re sober to take it could cost you hours that directly affect how well it works.
Other Factors That Affect How Well Plan B Works
While alcohol itself isn’t a concern for effectiveness, body weight is. Plan B becomes less effective in people who weigh more than 165 pounds. If you weigh 195 pounds or more, a different emergency contraceptive called ella is an option, though it also has reduced effectiveness above that weight. A copper IUD, placed by a provider within five days, is the most effective emergency contraception regardless of weight.
The bottom line: take Plan B as soon as possible regardless of whether you’ve been drinking. If you’ve already taken it, a drink or two a few hours later is fine. Just be aware that your body is already dealing with a hormonal disruption, and alcohol will make the physical side effects harder to manage. If you’re within that first three hours, skip the drinks entirely until you’re past the vomiting risk window.