Skip to main content
  1. Home
  2. Food & Drink

Why does coffee make me sleepy? How caffeine can leave you feeling tired

What to do when coffee has the opposite effect

By
Man who is tired
Andrew Neel / Pexels

Coffee is the most popular stimulant in the U.S., consumed by nearly 75% of Americans. As a long-time coffee drinker, there’s no doubt that it’s my favorite stimulant (even if its effects are unnoticeable due to my crazy high caffeine tolerance). Even though I crave coffee’s taste, with a slight bitterness and light sweetness, based on taste alone, I sometimes reach for coffee simply for a major boost of energy from its caffeine content.

At times, I feel perkier after a cup of coffee, but there are also times I’m struggling to stay awake. This phenomenon has left me questioning,” Why does coffee make me sleepy?” If you’ve felt that random wave of tiredness hit you after consuming caffeine, you might have asked yourself this question, too. The question of how coffee and tiredness are interrelated can get confusing, especially given coffee’s well-known reputation as a drink that keeps you awake. Here are a few reasons you might feel tired after drinking coffee.

Recommended Videos

Why does coffee make me sleepy?

person drinking coffee
Vlada Karpovich / Pexels

Regular coffee drinkers may experience the opposite of their desired effect after drinking coffee, leaving them more tired and sluggish than before their last cup. Sleepiness after drinking coffee doesn’t affect everyone; it may only affect you sometimes or not all. People who drink coffee regularly may also notice tiredness after coffee more than those who drink coffee occasionally. Here’s why.

Related

Effects on adenosine receptors

You may feel sleepy after drinking coffee because caffeine blocks adenosine receptors in the brain. Adenosine is an important brain chemical that impacts our sleep-wake cycles. Typically, adenosine levels will increase throughout the day and decrease during sleep, as molecules will bind to receptors in the brain to prepare the body to go to sleep. However, drinking coffee can interfere with this natural process and prevent adenosine from binding to the appropriate brain receptors.

Although you might feel fine immediately after drinking coffee, Adenosine receptors will begin to bind again as the caffeine wears off. Thus, you may feel a wave of tiredness rush in —  leaving you ready for a mid-day nap.

Caffeine tolerance

Caffeine tolerance frequently affects regular coffee drinkers as the body adapts to regular caffeine intake. As tolerance develops, the body will require more and more caffeine to feel those “stimulant” effects. The concept of “caffeine tolerance” is so real that some regular coffee drinkers wonder if there is even any caffeine in their cups. Studies have shown that the brain adapts over time to regular caffeine exposure. This means a person who drinks caffeine daily will produce more adenosine receptors, binding more adenosine and reducing the “stimulant” feelings from drinking coffee. I know “caffeine tolerance” all too well, which could be my sign to give matcha a chance instead.

Blood sugar levels

Most of us have felt an actual blood sugar crash at one point or another, especially after consuming a heavy meal (think post-Thanksgiving dinner). However, caffeine may also impact your glucose metabolism and blood sugar levels. In one study, researchers found that consuming 100mg of caffeine hurt glucose metabolism. While consuming coffee might not affect every person’s blood sugar levels, those with metabolic issues or Diabetes may find coffee makes them more tired.

Another component of why coffee may make you tired could be what you’re putting in your coffee. Many coffee drinkers have a heavy hand when adding sugar to their coffee or maybe consuming pre-packaged coffees that contain sugar. Hidden sugars in your coffee can impact blood sugar levels, leaving you feeling more tired after finishing your cup. Switching to sugar-free coffees, such as by adding zero-sugar coffee syrups, can help support healthier blood sugar levels.

The coffee sleep cycle

man sleeping
Ollyy / Shutterstock
Caffeine’s effects on adenosine receptors, a build-up of caffeine tolerance, and changes in blood sugars all contribute to why coffee makes us sleepy. However, perhaps one of the more obvious reasons for sleepiness from coffee is due to the never-ending “coffee sleep cycle.” Picture this — you’re tired from a stormy night of sleep, and you wake up and rush to consume two cups of coffee. Then noontime hits, and you feel sluggish again, consuming another cup of coffee. You make it to 3:30 p.m., where you consume one last cup of coffee (or two) to finish the work day. Before you know it, you’ve lost track of the number of cups you’ve had that day.
Sipping on all of this caffeine ultimately affects your sleep quality and cycle when it comes time to get to sleep that day. Studies show that caffeine can greatly impact a normal sleep cycle, making falling and staying asleep difficult. This contributes to a poor night of sleep, leaving you with more daytime sleepiness the following day. Then, the cycle continues as you reach for another cup of coffee to make it through the next day. While this phenomenon may not leave you tired immediately after drinking a cup of coffee, it’s a never-ending cycle that contributes to feeling tired, day after day.

Editors’ Recommendations

Topics
Emily Caldwell
Emily Caldwell
Contributor
Emily is a freelance journalist who focuses on food, beverage, health, fitness, and travel content. She loves to travel to…
How to steam milk: Perfect your technique for rich, creamy coffee drinks
Learn to steam milk like a Barista
steamed milk

As an aspiring barista, I've grown to understand the importance of steamed milk in making all of my favorite drinks. To learn how to make a cappuccino at home, I had to master the art of making steamed milk. Learning how to steam milk at home is difficult, but you'll need to commit to learning if you want to expand the types of coffee drinks you can make at home. Teaching yourself how to steam milk will allow you to experiment with all kinds of elaborate espresso drinks just like you order at the café -- from the cafe au laits to cappuccinos.
Steamed milk vs. frothed milk

As you experiment with how to steam milk, it's key to understand the slight differences between steamed milk and frothed milk. In the world of coffee-making, these two are often confused -- and I completely understand why. To help you know the difference, consider how you'd make a latte. The ratio of espresso to milk in a latte is usually 3:1, with espresso on the bottom, steamed milk on the top, and a light layer of frothed milk on the top.

Read more
80% of coffee drinkers say they can’t take it black, new study finds
Americans are having a hard time adjusting to black coffee
Black cup of coffee next to a pastry

A new 2025 Wake Up Survey, conducted by an independent research firm, Edelman Data x Intelligence, in partnership with Nestlé Starbucks At Home, found that Americans still crave coffee add-ins, including cream, sugar, or flavorings. The study, which followed the coffee-drinking habits of about 1000 U.S. adults (from January 22nd through January 29th, 2025), found that 79% refused to drink black coffee. Additionally, most participants consumed their first cup of morning coffee 30 minutes after waking up.

Not only did the Wake Up Survey determine that most coffee drinkers want a flavorful cup, but it also found that more than 3 in 5 coffee drinkers sought easy options to enjoy their favorite cafe coffee flavors from home. Researchers found that while many are drawn to the caffeine in coffee, most coffee drinkers found drinking coffee to be a relaxing component of getting ready in the morning.

Read more
Ground coffee vs. instant coffee: A battle of taste, convenience, and caffeine
Can you substitute ground coffee for instant coffee?
instant coffee

To a non-coffee drinker, ground coffee and instant coffee might look the same to the naked eye. Both appear as ground, brown powders. but only from a distance. But for everyday coffee drinkers like me, there's a big difference between ground coffee vs. instant coffee -- both in appearance, use, and, most importantly, taste. To me, instant coffee has a "coffee dust" or crystalized appearance, whereas ground coffee almost appears more like "dirt."

I like to consider myself an "open-minded" coffee drinker, as I firmly believe there is a time and a place for every type of coffee in my life. This means I'll gladly use both ground coffee or instant coffee, depending on the scenario. For me, ground coffee is perfect for everyday coffee brewing at home, but instant coffee is the ideal coffee product to take on the go. But what is the reason for the differences between ground coffee vs. instant coffee? Let's compare.
Ground coffee vs. instant coffee

Read more