Part of our Mushroom Coffee guide library.
Short answer: Coffee does not create energy; caffeine blocks adenosine, a natural substance that helps make you sleepy. When the caffeine wears off, that sleep pressure is still there. If you are short on sleep, coffee can only mask it, and caffeine late in the day can cut your sleep further, by about 45 minutes on average in a review of 24 studies. Regular drinkers also develop tolerance, so the morning cup may mostly undo overnight withdrawal rather than add a boost. Dehydration is an unlikely cause: in habitual drinkers, moderate coffee hydrated about as well as water.
It feels backwards: you drink coffee to wake up and end up wanting a nap. There is usually a reason, and most of them come back to sleep. Here is what research says about why coffee can make you tired, how to tell which reason applies to you, and what to change. For the sudden energy dip a few hours after coffee, see why caffeine crashes happen.
What you'll learn
- How caffeine works, and why tiredness can return when it wears off
- How poor sleep, late caffeine and tolerance make coffee feel useless
- Whether coffee dehydrates you
- What to try, and when tiredness is a reason to see a provider
How caffeine keeps you awake
Adenosine is a natural substance that helps regulate sleep; it is thought to build up the longer you are awake, adding to your drive to sleep. Caffeine works by blocking adenosine receptors, which reduces sleepiness (Reichert et al., 2022; McLellan et al., 2016). It does not remove the adenosine or repay the sleep you are missing. Caffeine peaks in your blood within about an hour and you may feel it for 4 to 6 hours (MedlinePlus); after that, the sleepiness it was masking can come back.
Reason 1: You are short on sleep
When people get their usual amount of sleep, caffeine mostly restores performance that sleepiness has dragged down rather than lifting it above normal, according to a review in Sleep Medicine Reviews (Roehrs & Roth, 2008). If you are running on too little sleep, coffee can cover it for a while, but it cannot replace it, and tiredness tends to win once the caffeine fades.
Reason 2: Caffeine is cutting into your sleep
A meta-analysis of 24 studies found that caffeine reduced total sleep time by about 45 minutes and sleep efficiency by 7%, and made it take about 9 minutes longer to fall asleep. A typical cup of coffee (about 107 mg) should be finished at least 8.8 hours before bed to avoid these effects (Gardiner et al., 2023). Large population studies also link regular caffeine intake with disturbed sleep and daytime sleepiness (Roehrs & Roth, 2008). The result can be a loop: worse sleep, more coffee, worse sleep.
Reason 3: Tolerance and withdrawal
Caffeine dependence develops at fairly low daily doses after short periods of regular use (Roehrs & Roth, 2008). When habitual drinkers go without caffeine overnight, they start the day in mild withdrawal, and some researchers argue that the alertness they feel after the first cup is mostly the reversal of that withdrawal rather than a true boost (Heatherley, 2011). If you cut back, withdrawal symptoms such as headache and tiredness usually start 12 to 24 hours later and can last 2 to 9 days (Juliano & Griffiths, 2004).
Reason 4: Is coffee dehydrating you?
Probably not. Caffeine is a mild diuretic (MedlinePlus), but in a study of 50 men who habitually drank coffee, four cups a day for three days kept them as hydrated as the same amount of water (Killer et al., 2014). One of the authors worked for a beverage company. Drinking enough fluids is still sensible, but dehydration is an unlikely reason your coffee makes you tired.
Reason 5: Something other than coffee
Tiredness has many causes, including sleep disorders, anemia or low iron, thyroid problems, depression, other medicines and alcohol (MedlinePlus). MedlinePlus notes that stimulants, including caffeine, are not effective treatments for fatigue and can make it worse when you stop (MedlinePlus). If you rely on more and more coffee just to get through the day, that is worth mentioning to a provider.
How to tell which reason applies to you
| If you notice… | Likely reason | Try |
|---|---|---|
| Coffee works for a few hours, then you crash | Masked sleepiness returning as caffeine wears off | More sleep; a smaller, earlier cup |
| You sleep poorly and drink coffee after lunch | Caffeine cutting into your sleep | Finish caffeine at least 8 to 9 hours before bed |
| The first cup only makes you feel "normal" | Tolerance and overnight withdrawal | Cut back gradually |
| You are tired no matter what you do | Something other than coffee | See a provider |
What helps
- Protect your sleep first. It is the one thing caffeine cannot replace.
- Move your last cup earlier. Aim to finish a typical cup of coffee at least 8.8 hours before bed (Gardiner et al., 2023).
- Use less, not more. If you want to break the tolerance cycle, cut back gradually; withdrawal is not dangerous but can be unpleasant (FDA).
- Try a gentler drink with less caffeine, such as green tea, matcha or a mushroom coffee blend. See how much caffeine is in a cup of coffee and matcha vs coffee.
- Get checked if tiredness lasts despite good sleep (MedlinePlus).
Common myths (quick reality check)
Myth: Coffee gives you energy. Reality: Caffeine blocks the signals that make you feel sleepy. It does not supply energy or replace sleep.
Myth: Coffee makes you tired because it dehydrates you. Reality: In habitual coffee drinkers, moderate coffee kept people about as hydrated as water.
Myth: More coffee will fix the tiredness. Reality: Extra caffeine can cut into your sleep and deepen tolerance, which can make tiredness worse over time.
Frequently asked questions (FAQ)
Why does coffee make me sleepy?
Caffeine blocks adenosine, a sleep-promoting substance, but does not remove it. When caffeine wears off, the sleepiness can return, especially if you are short on sleep.
Why does caffeine make me tired instead of awake?
Common reasons are too little sleep, caffeine late in the day cutting into your sleep, and tolerance, where the first cup mostly relieves overnight withdrawal.
Can you build a tolerance to caffeine?
Yes. Dependence can develop at fairly low daily doses after short periods of regular use, which makes each cup feel less effective.
Does coffee dehydrate you and make you tired?
Probably not. In a study of habitual coffee drinkers, four cups a day kept them as hydrated as the same amount of water.
How long before bed should I stop drinking coffee?
A 2023 meta-analysis suggests finishing a typical cup of coffee at least 8.8 hours before bed.
Is it normal to feel tired after coffee?
It is common, and usually linked to sleep or tolerance. If you are tired all the time despite good sleep, see a health care provider.
Related guides
- Caffeine withdrawal: how long it lasts and how to ease it
- How long does caffeine stay in your system?
- Why caffeine crashes happen
- How much caffeine is in a cup of coffee?
- Does decaf coffee have caffeine?
- Matcha vs coffee
- When to drink mushroom coffee
Disclaimer and when to seek help
This article is for general education and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. Our products are not intended to diagnose, treat, cure, or prevent any disease. Talk to your health care provider if you have ongoing fatigue, sleep problems, a heart condition or anxiety, are pregnant or breastfeeding, or take medication.
References
- Reichert CF, Deboer T, Landolt HP. "Adenosine, caffeine, and sleep-wake regulation: state of the science and perspectives." Journal of Sleep Research, 2022;31(4):e13597. doi:10.1111/jsr.13597
- McLellan TM, Caldwell JA, Lieberman HR. "A review of caffeine's effects on cognitive, physical and occupational performance." Neuroscience & Biobehavioral Reviews, 2016;71:294-312. doi:10.1016/j.neubiorev.2016.09.001
- Roehrs T, Roth T. "Caffeine: sleep and daytime sleepiness." Sleep Medicine Reviews, 2008;12(2):153-162. doi:10.1016/j.smrv.2007.07.004
- Heatherley SV. "Caffeine withdrawal, sleepiness, and driving performance: what does the research really tell us?" Nutritional Neuroscience, 2011;14(3):89-95. doi:10.1179/147683011X13019262348785
- Gardiner C, et al. "The effect of caffeine on subsequent sleep: A systematic review and meta-analysis." Sleep Medicine Reviews, 2023;69:101764. doi:10.1016/j.smrv.2023.101764
- Juliano LM, Griffiths RR. "A critical review of caffeine withdrawal." Psychopharmacology, 2004;176(1):1-29. doi:10.1007/s00213-004-2000-x
- Killer SC, Blannin AK, Jeukendrup AE. "No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population." PLoS One, 2014;9(1):e84154. doi:10.1371/journal.pone.0084154
- MedlinePlus (U.S. National Library of Medicine). "Fatigue".
- MedlinePlus (U.S. National Library of Medicine). "Caffeine".
- U.S. Food and Drug Administration. "Spilling the Beans: How Much Caffeine Is Too Much?" Content current as of August 28, 2024.
