Bad sleep after a night out?

You got home late, a little buzzed, crashed hard, and then woke up in the middle of the night with a dry mouth and no way back to sleep. The next day, you’re dragging. It’s one of the most common nights there is after going out, and the causes stack up: alcohol first, which knocks you out and then breaks up the back half of the night, a late bedtime, the music and adrenaline that take a while to wear off, late-night food, thirst, a room that’s too warm. And there’s one cause almost nobody counts: caffeine. The kind in a rum and Coke, a vodka Red Bull, an espresso martini, the coffee after dinner to keep going, or the energy drink you had while getting ready. Here’s how to sort it out, and how to keep the fun without losing the night.

Why do you sleep so badly after a night out?

Alcohol, first and foremost

It’s the main cause, and it’s well documented. Alcohol helps you fall asleep faster and makes the first part of the night deeper. But as your body clears it, roughly one standard drink per hour, the second half of the night falls apart: more wake-ups, lighter sleep, and less REM sleep, the dreaming kind, once the amounts go up (Ebrahim et al., 2013). That’s why it feels like you slept like a rock, and then not at all.

The rest of the night

• A late bedtime. The night is shorter, and you often wake at your usual time anyway: daylight, your bladder, the neighbors.
• Music, crowds, adrenaline. You come home with your heart still pumping and your ears ringing, and it takes a while to come down.
• Late-night food, the pizza on the way home included, still digesting when you’re trying to sleep.
• Thirst. Alcohol makes you pee more, so you wake up with a dry mouth, or to go to the bathroom.
• A room that’s too warm, especially if you’re crashing at a friend’s place.
• Caffeine, covered right below.

Caffeine, the one nobody counts on a night out

On a night out, people sometimes count their drinks, almost never their caffeine. Yet it’s everywhere:

• Cola mixers. A rum and Coke made with about half a can of Coke carries around 17 mg of caffeine, and Diet Coke has more (see how much caffeine is in a Coca-Cola). Three or four over the night add up to about a shot of espresso.
• Energy drink mixers. A vodka Red Bull made with a full 8.4-oz can is 80 mg, about as much as a shot of espresso (see Red Bull caffeine). Two of those, and you’re past a regular cup of drip coffee.
• The espresso martini, which usually contains a real shot of espresso, so roughly 60 to 80 mg.
• The after-dinner coffee to stay up before heading out, a classic with its own page: coffee after dinner.
• The energy drink while getting ready, to start the night strong.

The problem is that this caffeine comes in late. It works by blocking adenosine, the molecule that pushes you toward sleep, and its half-life is about 5 hours, often 3 to 7 depending on the person: half of what you drink late in the evening is still there five hours later, right when you’re trying to sleep. The two effects don’t cancel out. Alcohol already breaks up the end of the night, and caffeine that’s still active makes it lighter. For that exact wake-up, see why you wake up at 3 a.m..

Caffeine and alcohol: feeling less drunk without being less drunk

There’s another trap. Caffeine masks the feeling of being drunk without changing the alcohol in your blood: you feel more alert, while your blood alcohol, your reflexes and your judgment haven’t moved. As the CDC puts it, the effects of alcohol on your body don’t change when it’s used with caffeine, and feeling less affected can lead you to drink more than you meant to. It’s also why premixed caffeinated alcoholic drinks were pulled from the US market in 2010. And it’s why the “coffee to sober up” before getting behind the wheel doesn’t work: only time brings alcohol down, as does coffee sober you up? explains.

The test: your next few nights out

One night proves nothing; too much changes from one outing to the next. Run the test over two or three:

1. Pick caffeine-free mixers for the second half of the night: juice, lemonade, soda water, tonic, caffeine-free cola.
2. No coffee after dinner and no energy drink before going out, or make it decaf.
3. Change nothing else, as far as you can: same kind of night, same time home.
4. Rate your night from 1 to 5, and how you feel the next day.

If the night is clearly less choppy, the caffeine was part of the story. If nothing changes, it’s mostly the alcohol and the late bedtime talking.

If you sleep badly even on nights you don’t drink, or if drinking is starting to worry you, talk to your doctor. You can also call SAMHSA’s National Helpline at 1-800-662-4357: it’s free, confidential, and open 24/7.

How can you sleep better after a night out?

• A glass of water between drinks, so you get to bed less thirsty.
• Eat something during the night, rather than a big meal right before bed.
• Caffeine-free mixers for your last drinks, and skip the coffee to keep going if the night matters.
• A cool, dark room, with the blinds down if you’re planning to sleep in.
• The next day, keep your morning coffee on schedule, but don’t stack more in the afternoon to get through: the following night would pay for it.

Keep the fun, get your nights back

CaffIQ helps you see where you stand and take back control of your sleep, nights out included. The after-dinner coffee, the energy drink before heading out or the Coke in your drinks go in like any other drink, and CaffIQ estimates how much will be left when you get into bed, with a personal cutoff that tells you whether the next one still fits. And if your watch saves your nights to the Health app, the Sleep Lab in CaffIQ Pro puts them side by side with your caffeine, so you can see whether the link exists for you.

No need to give up nights out, or coffee. Usually, a caffeine-free mixer for the last few drinks and a decaf after dinner are enough, with the real coffee saved for the next morning.

CaffIQ provides general estimates, not medical advice. For any health question, consult a qualified professional.