Myth or fact

Should you wait 90 minutes after waking for your first coffee?

Short answerNo

By GyroscopeUpdated November 14, 20263 sources

No. There’s no evidence that a coffee right after waking causes an afternoon crash, or that waiting 90 minutes prevents one. A 2024 review of the research went through the reasons people give for waiting and found none of them hold up. The cup that changes your night is your last one, not your first.

Why people believe it

The rule spread mostly on social media, with advice to hold off anywhere from 30 minutes to 2 hours after waking. It comes with a story that sounds like biology. Your stress hormone, cortisol, peaks soon after you wake, so coffee then is wasted or makes things worse. Adenosine, the chemical that makes you sleepy, is still clearing out of your brain in the first hour, so caffeine should wait until it’s gone. And coffee too early sets you up for a crash after lunch.

Worrying about the first cup for your afternoon and your night is like checking the front door lock twice when the back door is open. The cup that reaches your bedtime is the late one.

What the evidence says

In 2024 a group of sports nutrition researchers published a review of 14 common questions about caffeine, and the 90 minute rule was one of them. They took each part of the story in turn.

• Cortisol. It does peak within about an hour of waking, and caffeine does raise it. In one study, about 3.3 mg per kg raised cortisol about 30% above placebo for an hour or two. But hard weight training soon after waking raises cortisol too, and by the same logic you’d have to avoid morning workouts, which the review said “makes no scientific or pragmatic sense”.
• Adenosine. The review called the idea that adenosine keeps falling after you wake “scientifically inaccurate and not supported by research”. Adenosine builds up while you’re awake and falls while you sleep.
• The crash. “There is also no evidence that caffeine ingestion upon waking is somehow responsible for an afternoon ‘crash’ or that delaying consumption would somehow prevent this if it did occur.”

What the afternoon slump really is

Adenosine builds up through the day for as long as you’re awake. A morning coffee keeps it off its receptors for a few hours, and by early afternoon about half the caffeine is gone and the adenosine you made all morning starts to land. Waiting 90 minutes moves that point later, but you’re still making adenosine the whole time. What caffeine actually does explains it.

The best case for it

If you like your mornings better when you wait, there’s nothing wrong with it. The trouble starts if the whole day slides. Three 8 oz coffees at 7am, noon and 4pm leave about 74 mg at 11pm. Push each one back 90 minutes, to 8:30am, 1:30pm and 5:30pm, and you go to bed with about 92 mg, over the line where a 2025 trial measured lost deep sleep.