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Why Does Coffee Make Me Sleepy?

By 04/16/2016Coffeecademy, Health

Caffeine is a stimulant that increases alertness and boosts energy levels. Caffeine itself doesn’t cause drowsiness. Coffee, however, is a complex beverage, and drinking it can make you feel tired at times. Here’s a look at why coffee can actually make you sleepy and fatigued, even though it’s caffeinated.

Adenosine Will Make You Sleepy When the Caffeine Wears Off

The caffeine in coffee blocks adenosine receptors in your brain from receiving adenosine, which is a neurotransmitter that causes fatigue. Although caffeine prevents your brain from receiving adenosine, it doesn’t stop your body from producing the neurotransmitter. Thus, when the caffeine wears off, there is a buildup of adenosine that will make you sleepy.

Caffeine isn’t making you sleepy, because it doesn’t impact how much adenosine your body manufacturers. It does, however, delay the effects of that adenosine so that you feel it all at once in a rush when the caffeine wears off.

Sweet Coffee Will Give You a Sugar Crash

If your coffee’s especially sweet, you may experience a sugar crash shortly after drinking it. Sugar is processed much more quickly than coffee, and it leaves you without energy after it’s used up by your body. If you drink coffee-flavored drinks that have lots of sugar but little coffee, you may actually be experiencing a sugar rush and crash, more than a caffeine boost.

Photo by Anete Lusina on Unsplash

Photo by Nathan Dumlao on Unsplash

Coffee Makes You Dehydrated

The primary reason why coffee makes you sleepy sometimes is likely because it’s making you dehydrated.

Coffee is a diuretic. In other words, it makes you need to urinate. Drinking it to stay awake can quickly lead to a vicious dehydrating cycle that actually makes you more tired. The cycle goes like this:

  1. You drink a cup of coffee and soon afterwards need to use the bathroom.
  2. When you go to the bathroom, your body loses water.
  3. When your body loses water, your blood thickens.
  4. When your blood thickens, it moves more slowly through your arteries and veins.
  5. As your blood slows down, it delivers less oxygen to your body.
  6. Without as much oxygen, you become sluggish.
  7. You may reach for more coffee to combat the sluggishness, thus starting the cycle again.

Because you’re drinking coffee, you likely aren’t drinking water to rehydrate yourself. At least, you probably aren’t drinking as much as you should be.

Additionally, coffee is a vasoconstrictor, which further compounds the problem. Coffee makes your arteries and veins get narrower. As they narrow, it only becomes more difficult for your thickening blood to flow through them.

You Can Limit the Effects of Coffee

If coffee regularly makes you sleepy, there are a few things you can do to limit its fatiguing effects:

  • Moderate your coffee intake. (The Mayo Clinic recommends having no more than 400 milligrams of caffeine a day, which is about 2 to 4 cups of coffee.)
  • Avoid coffee beverages with lots of sugar.
  • Drink plenty of water with your coffee.

Learn More About Coffee

On CoffeeCademy, we frequently write about coffee and its effects on the body. To get future updates, like us on Facebook where we mention each time we have a new post.

Author Scott

Scott is a professional writer for Driftaway Coffee. He worked as a barista for eight years, but today prefers to enjoy his beverages from the other side of the counter. When not drinking Driftaway Coffee, Scott usually has a mug of his own roasted coffee nearby.

More posts by Scott
  • RaybanM

    The issue doesn’t happen when I drink Tea, both without sugar. as such this is a Coffee, NOT caffeine specific issue.Lots of water does help, but particularly in mornings its a real crash. Im a Tea person mostly… will reduce coffee intake, way too much of a productivity hit.

  • Fidelma Vahey

    I love my real coffee every morning, 2 shot cappucinno, however, in the last year it makes me so tired, I’m gutted because I only have one a day, don’t like tea in the morning, don’t like decaf?

    • David Meeker

      Tea makes me nauseous

  • Jack Bowie

    Caffeine isn’t a specification attribute of coffee. It never has been and it never will be. As such levels of caffeine are a complete crap shoot using that delivery mechanism and often vary wildly even with the same brand. Quit trying to pretend you’re not a drug addict. Caffeine can be bought legally. Take a pill and dose precisely and properly. Take it with a decaf coffee if you must partake of that taste.

  • Christopher Lee Hall

    I’m pretty sure that when people are looking for reasons that coffee makes them sleepy they mean the effect of coffee not the hang-over. This article does not address the topic that its title advertises. Try harder author. Your article is worthless.

    • Sd

      The author says that coffee has no effect on the amount of fatigue signals the body produces. The dehydration caused by the diuretic that coffee is, is a direct effect of specific features of coffee you can’t find answers that aren’t there

  • Sudarshan Venkatachari

    I just drink one small cup of instant coffee per day and that very instance I feel sleepy….

  • RoadKillHeaven

    Sometimes I get drowsy right after I drink a double shot espresso.

  • Michael Hildebrand

    Hmm, what about this theory: if you have immunized yourself to caffeine and its stimulating effects, like I believe I have after regularly drinking a lot of coffee:

    (1) Wake up in the morning, perhaps still feeling tired and wanting some coffee to help wake up.
    (2) Brew coffee/espresso, drink
    (3) Maybe “not notice” much of a difference
    (4) Within 20-40 minutes, feel a “coffee-crash”, feels like you are even more tired than before
    Explanation: This feeling of extra tiredness, or “crash” you are now experiencing, is actually due to the drop-off from your 20-40 minutes of being stimulated by your coffee. i.e. the coffee is not “making you tired”, the effect from its caffeine is just not lasting long, and when it wears off you drop in your level of “stimulation” significantly, which in the end makes you think the coffee made you tired.

    Thoughts? I came up with theory after brewing and drinking a double shot latte this morning, and a quad shot latte during lunch as I wanted to ensure alertness while I worked. Within an hour of my quad-shot, I felt pretty tired, more than how tired I felt after my double shot this morning. This seems to fit my theory, as the quad shot had me at even higher levels of stimulation than the double shot, so the corresponding level drop after its caffeine wore off was greater, leading to a greater sense of tiredness.

    Also might be contributing, is the more caffeinated you are by your drink, the more energy your body is able to, and does, use. So when the caffeine wears off, you are left with a non-caffeinated body that also just used abnormally-high quantities of energy during the caffeinated state, leaving you with abnormally-less energy to continue your day.

  • BillinLaMesa

    I tend to get a remarkable case of the drowsies with the first few ounces of coffee I drink. This passes swiftly, & by the time I finish my cup, the boilers are lit again. This is especially noticeable if I have an alcoholic drink with lunch, & then coffee around half an hour later. I’m wide awake and feeling fine after lunch, but when we hit the coffee shop, the first few sips send me into la-la land. I actually get a bit narcoleptic for around 10 minutes. Then everything changes, & I’m back to normal again. I’m a fast metabolizer of caffeine, & believe there is some metabolite from the first few sips that causes this.