Health and wellness “thought leaders” commonly recommend waiting at least 90 minutes after waking before drinking your morning coffee. 

They claim this delay prevents caffeine from interfering with two of your body’s key chemicals: adenosine and cortisol.

Adenosine is a molecule that builds up in your brain during the day so that by night time you feel tired. Caffeine blocks adenosine’s effects, helping you stay alert and awake.

The argument for delaying your morning coffee claims adenosine levels are still dropping after you wake up, so caffeine won’t work as well. Wait a little longer, however, and adenosine supposedly rises to a point where coffee becomes more effective.

Cortisol, on the other hand, is a hormone that peaks naturally within an hour of waking. It helps you shake the cobwebs and start the day with energy.

Some believe drinking coffee too early prolongs this cortisol peak, disrupting your body’s rhythm and leading to an energy slump later in the day.

But a 2024 review published in the Journal of the International Society of Sports Nutrition found no evidence to support these claims. 

The researchers found that adenosine levels rise quickly after waking and stabilize within minutes—not hours—which means caffeine is just as effective first thing in the morning as later in the day.

And while caffeine can briefly elevate cortisol levels, this effect is minimal for regular coffee drinkers and doesn’t interfere with cortisol’s natural rhythm.

The idea that drinking coffee in the morning causes an afternoon crash doesn’t hold water, either.

Afternoon energy dips are a natural part of your circadian rhythm and are often made worse by meals—not coffee. Research also shows no link between regular caffeine consumption and daytime sleepiness. 

The researchers highlighted another major flaw in the argument for avoiding caffeine in the morning: lifting weights early in the day causes similar cortisol spikes to caffeine.

If avoiding caffeine were necessary to prevent you from disrupting cortisol levels, the same logic would mean you’d have to skip morning workouts. Not only is this scientifically unsound, it’s advice many of the coffee-skipping influencers ignore.

In short, the science shows no reason to delay caffeine intake in the morning. So, if you enjoy a morning coffee, go ahead and drink up—it’s an effective and harmless way to begin the day.