Six Reasons Coffee Can Make You Sleepy

Coffee can make you feel sleepy due to adenosine rebound — caffeine blocks adenosine receptors, and when it wears off, accumulated adenosine floods the system, causing a crash. Other causes include dehydration (caffeine is a mild diuretic), blood sugar fluctuations from sugary coffee drinks, and adrenal fatigue from chronic overconsumption. If coffee consistently makes you drowsy rather than alert, reduce intake gradually and consult a physician to rule out underlying conditions.

We know coffee mostly as our wake-up drink. We have one, two, or even three cups, and we’re ready to face our day. And while coffee has many different ingredients, it’s caffeine that receives the most attention. Verified Source Harvard Health Blog run by Harvard Medical School offering in-depth guides to better health and articles on medical breakthroughs. View source

Ingesting caffeine Verified Source Medline Plus Online resource offered by the National Library of Medicine and part of the National Institutes of Health. View source stimulates your central nervous system, which wakes you up and feels more energetic. However, what about when coffee doesn’t seem to wake you up and leaves you feeling sleepy instead? Has the caffeine failed you?

Save $500 On Any Mattress

Plus free shipping

Get $500 OFF Mattresses

Coffee can affect your body in various ways, and how it affects you is different for everyone. We’ve compiled a list of six reasons why coffee might leave you feeling sleepy.

Why Does Coffee Block Adenosine and Cause a Crash?

Caffeine works by binding to adenosine receptors in the brain, temporarily preventing the sleepiness signal from getting through — but adenosine keeps accumulating the entire time. When the caffeine wears off, that built-up adenosine floods the receptors all at once, producing a crash that can feel more pronounced than the tiredness you started with, particularly if you were already sleep-deprived before your first cup.

When you drink coffee, your stomach and small intestine absorbs Verified Source Harvard Health Blog run by Harvard Medical School offering in-depth guides to better health and articles on medical breakthroughs. View source the caffeine and redistributes it through your bloodstream to multiple parts of your body, including your brain. After caffeine reaches your brain, it sticks to your adenosine receptors.

Now adenosine Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source helps you feel sleepy and controls your sleep-wake cycle.

When caffeine binds to your adenosine receptors, your brain isn’t processing its adenosine, but that doesn’t mean it stops producing it. Once the caffeine wears off, accumulated adenosine floods your receptors — and if bad sleep habits are already working against your rest, that crash hits even harder.

Can Coffee Dehydrate You and Make You Tired?

Caffeine is a mild diuretic that increases bathroom trips, and at four or more cups per day the fluid loss can outpace what the water in your coffee replaces, leaving you mildly dehydrated. Dehydration causes fatigue, dry mouth, dizziness, and reduced concentration — symptoms that can be easily mistaken for a caffeine crash when the actual fix is simply drinking more water alongside your coffee.

In simpler terms, drinking a cup of coffee may cause you to use the bathroom more often. Verified Source Mayo Clinic Ranked #1 hospital by U.S. News & World Report and one of the most trusted medical institutions in the world. The staff is committed to integrated patient care, education, and research. View source If you drink a moderate amount of coffee (two to three cups), you may not notice anything, but if you drink four or more cups Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source of coffee, you may find yourself running to use the restroom.

If you lose more fluids than you’re drinking, you may feel tired as dehydration Verified Source Medline Plus Online resource offered by the National Library of Medicine and part of the National Institutes of Health. View source takes effect. Other symptoms of dehydration include thirst, dry mouth, dizziness, dry skin, and a lack of sweat.

However, coffee may not actually dehydrate you that much. As Harvard Medical explains, Verified Source Harvard Health Blog run by Harvard Medical School offering in-depth guides to better health and articles on medical breakthroughs. View source while caffeinated beverages may increase restroom visits, the water in the drink still contributes to your overall fluid consumption.

To counteract dehydration, drink plenty of water and eat foods that contain water, such as fruits and vegetables. When you’re exercising, sick, or experiencing hot, humid, or cold weather, you may need to drink more water than usual. If your dehydration symptoms include fainting, a sped-up heart rate, rapid breathing, confusion, or shock, seek immediate medical attention.

Is the Sugar in Your Coffee Making You Sleepy?

Sweetened coffee drinks — including those with syrups, flavored creamers, honey, or whipped cream — can trigger a blood sugar spike followed by an insulin-driven crash that leaves you more tired than before you drank anything. The coffee’s caffeine and the sugar’s energy spike arrive at different times and wear off at different rates, which is why a sweet afternoon latte can produce a noticeable slump within an hour or two.

If you drink coffee sweetened with whipped cream, honey, syrup, or plain old sugar, you might feel tired if a sugar crash hits you.

When your body ingests more sugar than it’s used to, insulin is produced to offset it. However, the insulin also causes your blood glucose Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source levels to drop—and your blood glucose, also known as your blood sugar, is your body’s main source of energy.

So as your blood glucose levels decrease, you feel a lack of energy that can tire you out. You may also feel hungry, irritable, anxious, sweaty, dizzy, or on edge as the sugar crash hits.

It may not just be the sugar in your coffee, either. If you have a sweet snack such as a cookie or drink your morning coffee with a glass of orange juice (which can have as much sugar as five or six oranges), you might feel a sugar rush and subsequent decline. It’s particularly easy to binge sugary drinks, as they don’t fill you up the way food does.

If you experience a sugar crash, try having some protein to balance out your blood sugar levels.

Read more about how sugar affects sleep.

Can Mold in Coffee Make You Feel Tired?

There is mold contamination in a significant portion of raw coffee beans, and the mycotoxins produced by those molds have been linked to chronic fatigue in separate studies. While mycotoxin levels in commercially sold coffee are generally within legal safety limits, people who are particularly sensitive to mold may notice fatigue or difficulty concentrating after drinking coffee that a healthy person wouldn’t react to in the same way.

A 2003 NIH study Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source examined 60 samples of raw, unroasted coffee beans (known as green coffee) from Brazil.

“Practically all samples (91.7%) were contaminated with moulds (sic),” the study noted.

Other NIH research Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source also examined coffee samples for mycotoxins, Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source a product of microfungi. Mycotoxins found in the samples included aflatoxin B1 Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source ochratoxin A; Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source however, the concentrations of mycotoxins were deemed “acceptable according to legal limits.”

And 2013 research Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source has linked exposure to mycotoxins to chronic fatigue. Those with chronic fatigue Verified Source Medline Plus Online resource offered by the National Library of Medicine and part of the National Institutes of Health. View source feel tired even after resting and may experience sleep problems. Other symptoms include dizziness and difficulty thinking or concentrating.

Does Caffeine Raise Stress Hormones and Cause Fatigue?

Caffeine doubles circulating levels of cortisol and epinephrine regardless of a person’s regular caffeine intake — meaning even your usual daily cup triggers a measurable stress response. Once that initial alertness from the adrenaline surge passes, the comedown can register as fatigue, particularly in people who are already running on elevated baseline stress from poor sleep or other lifestyle factors.

Stress can keep you awake at night, as anyone with stress-induced insomnia Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source knows. However, stress can leave you feeling tired Verified Source Medline Plus Online resource offered by the National Library of Medicine and part of the National Institutes of Health. View source or fatigued Verified Source Medline Plus Online resource offered by the National Library of Medicine and part of the National Institutes of Health. View source during the day. If you’re feeling stressed, you may want to sleep to process the experience, as you consolidate emotional memories Verified Source Medline Plus Online resource offered by the National Library of Medicine and part of the National Institutes of Health. View source during sleep.

We feel stressed in reaction to the stress hormone cortisol, Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source which signals our body to stay on high alert in response to a perceived stressor. Another component of our bodies’ stress response is epinephrine, Verified Source Harvard Health Blog run by Harvard Medical School offering in-depth guides to better health and articles on medical breakthroughs. View source commonly-known as adrenaline. As epinephrine travels throughout the body, the heart speeds up and we breathe faster to increase our alertness.

Now, a 2017 study found that ingesting caffeine doubled the levels of epinephrine and cortisol, regardless of whether the subject regularly consumed caffeine or not.

This means you can feel stressed after drinking a cup of coffee with caffeine, even if it’s the same amount you drink every day. And your body might translate that stress into sleepiness, once the initial stress response has passed.

What Are Caffeine Withdrawal Symptoms and When Do They Start?

If you regularly drink coffee and cut back abruptly, withdrawal symptoms including sleepiness, headaches, irritability, nausea, and difficulty concentrating can set in within 12 to 24 hours of your last cup and last anywhere from a few days to two weeks depending on how much you were consuming. Tapering gradually — reducing by about a quarter cup every two to three days — prevents most withdrawal symptoms from becoming disruptive to your day or your sleep.

As caffeine affects sleep, so too is sleepiness is one symptom of caffeine withdrawal, along with headaches, nausea, irritability, and an inability to concentrate.

You can feel withdrawal set in within 12 to 24 hours after you last ingested caffeine. Depending on how much caffeine you regularly consumed, symptoms may last only a few days or a couple of weeks.

If you want to quit drinking coffee and avoid caffeine withdrawal symptoms, try a gradual approach. Cut back on your consumption by ¼ of a cup every two to three days, or switch to green tea for less caffeine. Continue cutting back until you’re no longer consuming caffeine.

A slower approach can help you wean yourself off without impacting your daytime performance and ability to fall asleep quickly at night.

Should I Just Take a Nap If I Feel Sleepy After Coffee?

A short nap of 20 minutes or less, timed before 3 p.m., will often do more than another cup of coffee — research shows napping outperforms caffeine for cognitive performance, and it lets your body process the adenosine buildup that coffee was only masking. If you’re routinely relying on both coffee and naps to get through the day, that pattern more often points to insufficient nighttime sleep than a caffeine problem worth solving with more caffeine.

It’s tempting to reach for another cup when the post-coffee crash hits, but a short nap may actually do more good. Research Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source shows Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source that napping outperforms caffeine alone for cognitive tasks.

And a well-timed rest lets your body process the adenosine buildup that coffee was only masking! So if sleepiness hits, it can be worth it to grab a pillow and see if you lie down and catch some Z’s.

That said, naps aren’t a cure-all — especially if your bad sleep habits are quietly draining your baseline. If you’re regularly relying on both coffee and naps to get through the day, that pattern often points to insufficient or poor-quality nighttime sleep rather than a caffeine problem.

If you do decide to nap, keep it to 20 minutes or less and time it before 3 p.m. to avoid disrupting your night. A power nap in that window gives you the alertness boost without sleep inertia or a delayed bedtime.

Some people even find a coffee nap — drinking a cup right before a short rest — more effective than either alone, since the caffeine kicks in just as they wake up.

If you feel sleepy every day regardless of how much coffee you drink, it may be worth examining why you can’t nap when tired even when exhaustion seems obvious, or looking at the best nap length for your schedule to make rest work harder for you.

See also how remote workers are napping during the day.

Frequently Asked Questions

How long does it take for coffee to take effect?

You’re likely to feel the caffeine kick in as little as 10 minutes, Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source and the amount of caffeine circulating in your blood peaks within 30 to 90 minutes Verified Source Harvard Health Blog run by Harvard Medical School offering in-depth guides to better health and articles on medical breakthroughs. View source after consumption. While you may stop feeling the effects within a few hours as the caffeine is metabolized, it takes many hours for caffeine to completely leave your body.

Can caffeine not affect you?

If you regularly consume caffeine, you may stop noticing the effects of your usual cup of coffee as you develop a tolerance. Caffeine tolerance can also vary by individual.

Is caffeine bad for your heart?

Numerous studies have examined the link between caffeine, coffee, and coronary heart disease, but results vary. Outside factors such as other dietary choices may have affected the results. The American Heart Association says that drinking one or two cups of coffee a day should be all right.

A 2017 review Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source noted caffeine “is more often associated with benefit than harm for a range of health outcomes across multiple measures of exposure, including high versus low, any versus none, and one extra cup a day.”

How does caffeine affect your sleep?

Caffeine close to bedtime can keep you from getting a good night’s sleep. If you ingest caffeine six hours Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source before bed, you may still feel the effects when you turn in for the night. The half-life of caffeine, or the time it takes for your body to get rid of half the caffeine you ingest, varies from three to seven hours in adults. Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source

How do you flush out caffeine?

Drinking more water, exercising, and eating are all common recommendations for a mild caffeine overdose. Drinking herbal tea and practicing breathing exercises may also help you feel calmer.

Did We Help?

Coffee contains stimulating caffeine, but it has its limits. You might feel tired as you feel the effects of adenosine build-up, dehydration, decreased blood sugar, and more. The reasons you feel sleepy can vary, but the solution might be getting a better night’s sleep by watching what you eat before bed.