If you’re planning to drive the day after you go out drinking, be careful. You can still be drunk the next day, and it is possible to get a DUI.

One issue is that your blood alcohol concentration (BAC) doesn’t actually fall that quickly. For a 160-pound man who has six drinks, it can take nine hours for his BAC to drop back to zero. If he just sleeps for a few hours and then tries to get up for work, that alcohol isn’t out of his system yet.

It’s also easy to underestimate how much you drink. For instance, one “drink” is a single 12-ounce beer of around 5% alcohol. If you drink a craft beer that is 10%, that’s two drinks — not one. So, if you went out with friends, started with a shot, drank two beers, and then had one mixed drink as the night wound down, that’s already six drinks. If feels like four, but it’s not.

Another problem is that researchers have found that your hangover can bring on the same symptoms as being drunk. For driving, this means that you may have slower reaction times or make mistakes you wouldn’t when feeling a bit better. So, just being hungover could be enough for the police to pull you over on suspicion of drunk driving. If you then still have alcohol in your system because you didn’t wait long enough, you could definitely get arrested on DUI charges in the morning.

This is often very surprising to the drivers who get arrested. If it happens to you, it’s important to look into all of the legal defense options that you have.