“What happens in Vegas stays in Vegas” has become the city’s defining slogan, but The Hangover and its ilk have pointed to a possible new one: “Sometimes, it’s hard to tell what happened in Vegas. Shoot.” So if you wake up in Vegas to find a large, unidentified red stain on your carpet, stay calm. You’re not the first person to do this. Las Vegas carpet-cleaning services are just a phone call away.

Perhaps most importantly, we have some tips for figuring out if it’s a wine stain or if you, once again, tried to donate blood to yourself.

To Figure Out What It Is

Search the area around the stain. Do you see a wineglass? A handwritten sign that says “This is blood ;-)”? These are essential clues.

Look through your phone. Maybe you have pictures of last night.

Rewatch The Hangover. It’s full of helpful tips, maybe. It’ll at least inspire you to check your room for tigers.

Take time for introspection. Do you like wine? Do you feel hungover? Are you in pain, the bleeding type of pain?

Look in the mirror. Check yourself for wine mouth or for being a ghost now. Both are key clues.

Scrape the stain with a blunt knife. Gross but true—if chunks come off, it’s probably blood.

Once You Know What It Is

Consider how fresh it is. Fresh stains are easiest to remove—a quick Google search will recommend soaking them up with salt, spraying them with cold water or a gentle bleach solution, and various other quick fixes.

Then, regardless, call an expert. You had a crazy night last night. The pros at local carpet-cleaning companies will handle this better than you will. And they’ll only ask the strictly necessary questions, like “Do you want a hug and an Ibuprofen?”