Science Questions

Why does coffee make me sleepy?

Tue, 15th Oct 2013

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Matt Burnett asked:

Why is it that when I drink coffee it can make me more sleepy? Other people seem to drink coffee and wake up!


We posed this question to the brain panel.

Mike -   It depends on the time course.  Id be surprised if somebody would Sleeping Studentdrink a cup of coffee then immediately feels sleepy.  But I think its perfectly reasonable to feel sleepy a little bit later on because what's happening when you drink the coffee is that caffeine is complicated but its main effect is to block the action of a transmitter called adenosine which is a sort of dampening down a transmitter if you like in the brain.  So, when you block the effect then you feel more awake.  Later on, when the coffee effect wears off after it gets eliminated in every 4 hours or so, so when that's gone, the adenosine is still chugging along there and then that may then switch the other way so you feel more sleepy.  So, I dont know of a circumstances where you would drink coffee and then suddenly feel sleepy.

Bill-   Except perhaps if you had a strong association with coffee as a thing that you took next to going to sleep.  Like children here, nursery melodies and they're put to sleep by it.  If you had a routine in which you drank coffee and then went to sleep, it may be a signal to sleep and would help you get to sleep.  Is that possible?

Hannah -   Or maybe he associates coffee with incredibly boring activities like being in the office.

Katie -   Feeling really tired?

Hannah -   Maybe there's other listeners out there who experiences also.  If so, wed like to hear from you. 


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I've always thought that coffee can cause a spike in alertness, followed quite soon afterwards by a crash. 

Perhaps heavy coffee drinkers are also often sleep deprived, or perhaps don't get "good sleep", causing additional rebound drowsiness.  CliffordK, Fri, 25th Oct 2013

My guess is that this person is just one of those people who don't seem to be affected by caffeine, or need very large doses for it to take effect.

Then the sleepy effect would be caused by simply just having a warm drink, which often makes people tired. But would work just well with any hot drink like tea or hot chocolate.

If it turned out not to work with other hot drinks, obviously this theory wouldn't work, Super Hans, Sun, 27th Oct 2013

I'm sure I heard Chris (or maybe it was Dr Karl) say once that in some people, coffee can stimulate the part of them that wants to sleep, thus making them sleepier. I'm sure when the doctor described it it was much more scientific and lucid than that, but that's the message I took from it.

I sometimes wonder whether one can develop a dependence on caffeine which means they are intrinsically more tired all the time, and drinking coffee just brings them back to a "normal" level of background tiredness.

Also, if I drink coffee at night, I get tired because it's night and I want to go to bed. I don't think the coffee has a major effect on this (not as much as my kids anyway  ) bizerl, Mon, 4th Nov 2013

Yes, I think that is a major component of caffeine addiction.  That once addicted, one is no more alert than if a person wasn't addicted.  Just one has to have the coffee boost to get back to normal.

Add a little sleep deprivation, and the coffee may be counterproductive.

I have been mostly off of coffee & caffeine for quite some time.  But, there seems to remain a little bit of "brain fuzz" that I don't think was there before I first got addicted to coffee. CliffordK, Tue, 5th Nov 2013

I can't drink coffee. If i do drink, i need only one cup and my body crashes. First of all, it causes emptying my bowel, and secondly, i want to sleep. I remember i have had days in my past that coffee have made me more alert but thats years ago. I actually stopped to drink coffee for years and now tried to start it again - i couldn't - i can't see any positive effect in it. I could drink cup of coffee in the evening and go to sleep. Perhaps it is adrenal system and cortisol which are going over. luckoo, Fri, 15th Nov 2013

I have this problem sometimes, not all the time. I drink about 2 cups of coffee a day, generally in the morning, but some mornings almost as soon as I have drunk my cup of coffee (ie within half and hour and often before I have finished the cup) I feel an overwhelming tiredness - my eyes get really droopy feeling, my body feels really heavy and I feel like I can barely function... Its strange because its not everytime, I have also had the experience where after a strong cup of coffee I am bouncing off the walls... so its NOT because I'm a person whom caffeine doesn't affect at all. I'm still trying to find out why! Angie, Thu, 2nd Jan 2014

Nice to see this topic being discussed. I too find coffee makes me sleepy. I've never had any sort of 'high' or increased alertness from it. It's not that I'm addicted - I often rarely drink it. But when I do, I get sleepy. This was most noticeable when I tried caffeine tablets one day, to keep myself awake in work. On taking them, they had no effect, but a few hours later, I was more tired than ever, and could hardly seem to keep awake, so the 'warm drink' affect doesn't seem to be applicable either. I've heard it suggested that I may be slightly allergic to caffeine, and that the response is therefore a typical response when the body is trying to deal with toxins. Any thoughts on this? Cheers, Jamie Jamie, Mon, 6th Jan 2014

Yes I too get tired when I drink coffee. Almost instantly, I am new to coffee so it bring a habit before bed can be ruled out. Camren, Thu, 9th Jan 2014

Theobromine may be the culprit as a vasodilator. Caffeine is broken down and metabolised by the liver into theobromine, paraxanthene and theophylline. This may ultimately have to do with how well caffeine is metabolised by the body. alilfroggy, Mon, 13th Jan 2014

I drink coffee from the time I wake up untill I fall asleep at night. It makes me so sleepy I start yawning while I'm drinking it and I get my normal 7 hours or more of sleep. I just assumed it had the opposite effect on me because of how much I drink it. (7-10 cups normally per day ) Chrissy, Mon, 13th Jan 2014

For me when I drink coffee. It also makes me sleepy. I don't get boost what so ever. I mean after drinking it the next 20 to 30 mins i am struggling to stay awake. I am a medical student so I assumed that maybe it was just me being too sleep deprived and the dosage wasn't strong enough. So after exam period when I got some rest my friends and I decided to try it out. So i took some when I wasn't sleepy and it wasn't even near the time I usually go bed. It was approx. 6:30 pm and i usually go bed after 2 or so in the morning. Taking it at 6:30, i fell asleep near 7:00 pm I don't know why it is having this affect on me, but this wasn't always the case. In the past like earlier last year it did its job and perk me up. Maybe my body has developed some tolerance to it, receptors to caffeine might have become less sensitive. If that is the case though, i would expect that coffee would just then dont have any effect on me. Surprisingly it flipped the scale and went from perking me up to the opposite, making me sleepy. Anthony, Wed, 15th Jan 2014

Interesting discussion. I occasionally have a cup of coffee, mostly just because I like the taste, and often feel myself sleepier than before I had had it. And I'm talking one cup. In the morning. Not sure if it's some kind of placebo effect or if other factors around me are actually what's causing me to become tired. The only thing coffee does seem to do for me is make me pee a lot. Then again, several things that affect most people don't affect me... Vitamin B12? Nah. I suppose I'm just not sensitive like that. Miller, Thu, 16th Jan 2014

If I am drinking instant coffee I seem to perk up, but for example if I drink instant when I am sleep deprived I'll perk up, but then a few hours later I'll feel more tired than I think I would have otherwise. However - if I make Stove-top Italian 'espresso' coffee that can perk me up like almost instantly for about an hour - quiet extremely so, I get touch hyper and giggly and in a general good mood, then after the hour is up I'll feel sleepy, but the good mood seem to retain. Which is nice. I think this especially true at night, however I try to avoid drinking coffee 3 hours before bed. Doesn't Coffee give you a seratonin boost? I am really no expert in these matters, but doesn't your brain convert Seratonin into melatonin when the body clock tells it too? If you have extra serotonin, I imagine that melatonin is more readily available? So you feel sleepier? Just a guess. Tim, Sat, 18th Jan 2014

I too get tired and sleepy after minutes of drinking coffee. I don't drink coffee often, only when I feel the need to like when I need to study for an exam or when I wasn't able to sleep. I find that within 2 hours or possibly less than an hour, my eyes would feel really heavy and instead of feeling pumped to do some tasks, I would be nodding my head off while studying, for example. Even if I drink 2 glasses with good amount of coffee (I try to put a tbsp or a bit more to perhaps counteract the sleepiness & lots of sugar for added energy ), it still makes me sleepy. There was one or two times though, that I would feel really sleepy first ( or take a nap less than half an hour) then after that, I'm gonna be awake and focused on studying. Otherwise, I would call it a night and forget studies! And, this only happens when I drink coffee. I don't feel sleepy when I drink other hot substances such as hot choco or tea. Also, when it's not summer break I usually get less than 7 or 6 hours of sleep. Sleep deprived ? Ange, Tue, 21st Jan 2014

Ive always felt extremely sleepy within 30 mins after drinking a cup of coffee. I started drinking it in university when I wanted to stay up late, but it only put me out. I feel like my vrain just shuts down and my body is heavy with sleep. I'm only 26 and I love to drink coffee, but it still puts me out quick! Nicole, Tue, 21st Jan 2014

Hi.. I have the same issue about coffee.. But in my case I feel so tired and sleepy right after a few sip.. i can't even finish a cup. I would start to yawn and my eyes would be watery from feeling so sleepy. The weird part is I tried drinking instant coffee and I don't feel sleepy. Tried drinking starbucks frap or any brewed coffee and I'd instantly feel like crap. Social_butterfly15, Thu, 23rd Jan 2014

I too feel sleepy after drinking coffee i only drink it when i cannot fall asleep Aliyya, Fri, 24th Jan 2014

Happens to me too. I drink coffee to wake up with my two and a half yr old. at first I'm awake buthcrash because im awake and playing with my daugter doing chores running errans. amberrrr, Sun, 26th Jan 2014

Ditto. I realized this years ago when I worked odd hours and then again in many years of school. Every time I drink coffee, regardless of the time of day I get drowsy. My mother has had at least three cups a day for years and likewise for my father. However, for me it just makes me want to fall asleep. I even tried drinking it in the mornings consistently for a few weeks. As soon as I stopped drinking it I realized I wasn't as tired. I assumed I was alone, crazy and it was some paradoxical effect. Nice to know I am not alone! Frank, Wed, 29th Jan 2014

It's not just coffee for me. Anything with caffiene in it makes me drowsy and not in and hour or two but like 10 minutes or so James, Thu, 30th Jan 2014

This happens to me at times. I dont coffee very often. I usally use tea as I think a caffiene overdose makes me more tired whislt a small amount (like tea) helps me get through incredibly boring tasts without the fatigue afterwards Dale, Mon, 3rd Feb 2014

I take a nap nearly every morning after a cup of coffee. Don't have a clue why. If I get up out of bed I may not nap but I will still get drowsy. Ron, Mon, 10th Feb 2014

I'm one of those people that immediately wants to sleep after drinking coffee. I've never felt any sort of caffeine 'high' or alertness after consumption. Not even from my first cup, ever. Sometimes I end up drinking two cups and can't keep my eyes open within 20mins of beginning the drink. Not sure why.. Eley, Tue, 11th Feb 2014

I have always felt sleepy and more tired after consuming caffeine, no matter if it's in coffee or energy drinks. I seem to get the feeling that I can relax more easily with caffeine and therefor get sleepy. When I can't sleep I take 3 double expressos or something like a gult shot and 2 Redbulls. I've never had a suger rush either. My theory is a natural need for stimulation, that when caffeine gets the synapses busy, The natural need for stimulation is fufilled and this inner disturbance is satisfied and the Boyd is therefor able to relax more. Frederik Agge Ronex, Tue, 18th Feb 2014

I definitely feel sleepy right after I drink coffee, but I also have this feeling whenever I consume any type of really warm liquid. It doesn't matter if it's warm milk, herbal tea, green tea, black tea, cocoa, soup or plain hot water but warm things make me sleepy. Vika, Sun, 2nd Mar 2014

When I drink coffee I feel sleepy straight away unless it's caffeine free why is this David , Mon, 3rd Mar 2014

Usually people with ADHD get tired with caffeine. I'm one of those people. I have to avoid drinking caffeine before I drive, or I will doze off behind the wheel. It's so frustrating! There are no stimulants I can take to help me stay awake, ever. Lori, Mon, 17th Mar 2014

Usually people with ADHD get tired with caffeine. I'm one of those people. I have to avoid drinking caffeine before I drive, or I will doze off behind the wheel. It's so frustrating! There are no stimulants I can take to help me stay awake, ever. Lori, Mon, 17th Mar 2014

At work feeling fine. I thought a cup of coffee might perk me up, give a little motivation. By the time I got to the bottom of a cup of strong black coffee, I could barely keep my eyes opened. Repeated the experiment. Same results. Tried it in the morning on my day off. Second cup causes drowsiness. I used to be a 2 pot a day drinker, but cut way down over the years due to decreasing quality and increasing prices. Martymo, Fri, 21st Mar 2014

My roommate drinks coffee and then falls asleep instantly in the mornings. Caffeine seems to have the reverse effect on them. I drink coke to wake up. We both go to bed at the same time every night (my meds require it) and get 7-9 hours of sleep each night. They still have to take a nap every morning and nothing's helping. TWS, Mon, 7th Apr 2014

hey when ever i drink a coffee or energy drink in about 5-10 min i get rather sleepy from it and it does not wake me up in the slightest :( would any of you know what that is? Charles, Wed, 23rd Apr 2014

4 hours? whao!!! I think I am like this gentleman or worse, although I sleep very easily (I don't turn around in bed for hours before falling asleep), I think coffee has a sleeping pills effect on me. I even tried double espresso once but sometimes I am nodding my head as soon as I finish the coffee. May be we are special :) Mamou Adam, Tue, 29th Apr 2014

I have to take a caffeine tablet everyday. Within about 15 minutes after taking it I feel totally wiped out and exhausted, no matter what time of day I take it. This usually lasts about 3-4 hours and then I'm able to move on with my day. It's not good. It's not a spike, it's an instant crash. I do the same thing watching action movies! The more action the sleepier I get! I ALWAYS fall asleep during action flicks and usually right when the hardcore stuff starts rolling. My sister is the same way. Anyone have an explanation for me? HH, Wed, 30th Apr 2014

Stimulants have different effects on ADD and ADHD sufferers. Personally, when I take stimulants, I feel calm and centered. This is true for caffeine, most energy drinks, the occasional dabble into cocaine. If you combine that feeling with a bit of sleep deprivation (also a common side effect of ADD) and a belly full of warm liquid, and sleep is right around the corner. I've fallen asleep in my chair at the coffee shop more than once. Tyce, Thu, 1st May 2014

I get very sleepy when I drink coffee at any time of day. Alyssa, Tue, 6th May 2014

Hello, I actually have this same issue no matter the time of day if I drink coffee I suddenly get the overwhelming urge to just take a nap. I've found that this happens, to me anyway, because it's warm. The warmth I get from a fresh cup of coffee relaxes me and makes me comfortable enough that I want to rest. I've tested this with ice coffee, hot tea, and ice tea. The cold beverage wakes me up more even if the tea had no caffeine. The hot tea, like the coffee, made me want to sleep. Road, Sat, 10th May 2014

I drink coffee and immediately get tired. Same with onions. I eat them and they make me tired right away Vhicks, Mon, 12th May 2014

I don't drink coffee often, maybe once a week, but when I do it can put me right to sleep! I start feeling very tired even before I'm finished my drink! I've always wondered why. Any ideas? Darya, Mon, 9th Jun 2014

I am not a big coffee or caffeine drinker. I'll have a cup of coffee a few times a week or if I'm working swing shift. About 10 minutes after I have a cup of coffee, my body instantly feels weak and my eyes start to droop. Every time I have any sort of caffeine this happens. I don't know why I still drink coffee, it tastes good to me, but my body has weird affects with it. It doesn't wake me up. So if I can't fall asleep at night I instantly go for a cup of coffee. Court, Wed, 18th Jun 2014

Coffee relaxes me, drops my blood pressure (measured/confirmed by MD ), and can make me fall asleep within 30 mins or less after consuming it. I'd also like to understand why. This happens Even if I'm well -rested. Chanel , Thu, 10th Jul 2014

I immediately feel increasingly tired after drinking caffiene. I recently got back from a road trip where I consumed copious amounts of coffee and Red Bull and then fell promptly asleep, which was not good for driving. I guess in some people it just has opposite effects. Clarity, Wed, 23rd Jul 2014

I also drink coffee very rarely, mainly because I dislike the taste of all except the Mocha flavours but I do regularly take caffeine pills known as Pro Plus. My Sleep pattern is sporadic but I also function a lot better on 4-5 hours sleep than I do on 6-8 and I also have a very high metabolism. I to feel extremely sleepy within 30 mins of drinking even the exceptionally strong coffee Swazzy, Sat, 23rd Aug 2014

I think there may be something to how coffee reacts with ADD brain wiring. I was not diagnosed ADHD, so, dont have the hyper issue being thrown in reverse by a stimulant. I too get very drowsy while drinking coffee. Less often, I might get a short and very temporary boost, followed by the drowsiness. I have dozed off at my desk at work for a few seconds while consciously fighting to stay awake. This after drinking 2 to 4 cups of coffee each morning. The other benefits I see mentioned, that includes intestinal regularity, I have experienced as well. It also helps clear my throat in the AM from allergy generated sinus drainage. Geez, it is complex! Steve, Fri, 12th Sep 2014

I have recently started having coffee as my exams are going on.. It makes me sleepy. :( before i used to having tea when needed,but same result.. It made me sleepy in place of waking me up.. SaDaF, Tue, 16th Sep 2014

Oddly enough; I frequently drink multiple shots of espresso etc prior to meals to stimulate my digestion which it seems to help. But when I drink coffee or tea in the evening or at night it also makes me drowsy and does not negatively affect my sleep. Mystgreen, Tue, 7th Oct 2014

I found this article because I wondered why the drowsy effect of coffee was so instantaneous and like clockwork for me. It happens 10 to 20 minutes after I drink it. I even had a micro sleep just now, sitting up with my eyes open, shortly after drinking a cup. Before this, I was wide awake and full of energy. I just wanted to drink the coffee for its taste. Other hot drinks and instant coffee DO NOT do this to me, it's specifically plunger coffee or espresso. I have also had paradoxical reactions to other substances, such as a sleeping pill gave me insomnia, it was impossible to sleep for hours, and tequila acts as a stimulant but other spirits are a depressant. Ben Benson, Wed, 8th Oct 2014

I too suffer from this, I can drink 2-3 cups of coffee and fall into a deep sleep within minutes. Seems to have the opposite effect on me! J McDonald, Tue, 28th Oct 2014

I also suffer from this problem. I've read that coffee makes you pee a lot, which makes you dehydrated, your blood thickens, causing you to feel fatigued and fall asleep. Hope this helps! Jenoir, Tue, 28th Oct 2014

I drink rockstar blueberry high caffeine energy drinks and even while drinking them I fall asleep I sleep minimum 9 hours a night and usually get really tired and nap a couple hours in afternoon hannah, Sun, 9th Nov 2014

I had a professor that told me once that getting sleepy after drinking caffeine is a possible sign of a rare form of diabetes. (She had that form of diabetes) Thomas, Mon, 17th Nov 2014

Coffee makes me sleepy too and the days I have less I am much more alert. Tjspoerer, Tue, 18th Nov 2014

I don't drink coffee at all generally, but if on the rare occaison I do, I start immediately feeling drowsy and need to sleep This has always been the case with me I always thought my body/brain was wired differently Rhea , Tue, 18th Nov 2014

I can drink coffee and immediately feel sleepy. In fact its 12:57 a.m. I have a flavored 16 oz cappuccino with three little shots which are supposed to each equal one shot of espresso (*each*.... and there are three in this cup) And i am falling asleep -hence me finding this through a google search. -lizz- lizz, Thu, 27th Nov 2014

I drink 1-2 mugs of coffee every morning, and I have been doing that since High School. But I never drank it for the caffeine or for waking me up, I drank it for the sweet taste of coffee with sweetened liquid creamer. On the infrequent chance that I brew an additional pot of coffee (2 more mugs) for an afternoon drink I feel sleepy. And I only feel sleepy when in the afternoon. Even rarer is if I choose to drink coffee at night (say I'm out with friends or studying in the library or a coffee shop), it has no effect on me and it does not affect my sleep and I do not experience any caffeine crashes. I drink plenty of water throughout the day to keep hydrated and at meals, I drink one glass of fruit juice and then the rest are glasses of water. But if I miss my morning coffee I feel no symptoms of withdraw or headaches. Nick, Wed, 3rd Dec 2014

I drink 1-2 mugs of coffee every morning, and I have been doing that since High School. But I never drank it for the caffeine or for waking me up, I drank it for the sweet taste of coffee with sweetened liquid creamer. On the infrequent chance that I brew an additional pot of coffee (2 more mugs) for an afternoon drink I feel sleepy. And I only feel sleepy when in the afternoon. Even rarer is if I choose to drink coffee at night (say I'm out with friends or studying in the library or a coffee shop), it has no effect on me and it does not affect my sleep and I do not experience any caffeine crashes. I drink plenty of water throughout the day to keep hydrated and at meals, I drink one glass of fruit juice and then the rest are glasses of water. But if I miss my morning coffee I feel no symptoms of withdraw or headaches. Nick, Wed, 3rd Dec 2014

ADD & ADHD If it makes you drowsy almost immediately it is not a crash or anything similar. Those who mentioned ADD and ADHD are correct. Stimulants all effect ADD and ADHD including caffeine. Drinking something with caffeine can focus and calm those with the conditions, even aiding in sleep. University studies have shown caffeine may be a viable option in replacing heavy stimulants like Methylphenidate in children and adults with ADD and ADHD. M, Wed, 3rd Dec 2014

I fall sleepy immediately with coffee. I find it helps me concentrate on sleeping and eliminates my rapid random thoughts that tend to keep me awake. Guest , Mon, 15th Dec 2014

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