Why Does Coffee Make Me Sleepy?

Coffee Makes You Sleepy: 8 PROVEN Reasons Why it Happens

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It is usually believed that caffeine is the most extensively used stimulant in the world. However, it has different effects on different people. Caffeine is a stimulant that increases alertness and vigor after use. But what about those times when your morning brew does not do the trick and you end up feeling drowsy instead? Could it be that the caffeine is not doing its job? Each person responds differently to coffee and its potential physiological effects. We have listed the following reasons why coffee may cause you to feel drowsy.

Summarized Answer: Coffee makes you sleepy because it prevents adenosine from having its effect of keeping you active. Moreover, coffee can make you sleepy because you carry a high sleep debt as well as addiction to caffeine which builds up the tolerance. The Diuretic Effect of coffee is also an important reason why coffee makes you sleepy. Lastly, sugar crash, withdrawal of coffee, and natural energy dip are also few of the most important reasons why coffee puts you to sleep.

Why Doesn’t Coffee Wake Me Up?

The following are medically-proven reasons why does coffee make you sleepy. Follow the mentioned-reasons and uncover the ways in which you can avoid this from happening.

Coffee Prevents Adenosine From Having Its Effects

Coffee Prevents Adenosine From Having Its Effects

The body produces its neurotransmitter adenosine, which has a sedative effect on the Central Nervous System (CNS) and signals the brain to shut down and relax. While awake, its production exceeds its elimination, leading to sleepiness and the need to nap. It is eliminated during sleep, leaving us with significantly reduced adenosine levels upon waking and beginning the process all over again. This is one mechanism by which our body controls its 24-hour sleep/wake cycle.

However, caffeine alters the situation. By binding to the adenosine receptors in your brain, caffeine prevents adenosine from exerting its drowsiness-inducing effects. However, even when you are awake, adenosine continues to accumulate. Therefore, when your body metabolizes all the caffeine you have consumed, and adenosine can again connect to those receptors, you will experience not just the exhaustion you had before, but also the additional tiredness that has been building up.

For this reason, you can feel more drowsiness after the effects of coffee have worn off than before you drank it. However, it is not the caffeine that is to blame. Your body has built up a natural tolerance to sleep, and you are starting to feel it.

Although adenosine is known to cause drowsiness, a study by British Pharmacological Society shows that persons who frequently drink coffee have a higher than average number of adenosine receptors. As a result, they are more susceptible to its effects. You will feel very weary and have an overwhelming desire to have another cup of coffee after the effects of caffeine wear off and adenosine can resume its normal function.

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High Sleep Debt

High Sleep Debt

A person’s “sleep debt” is the amount of sleep they have owed their body in the previous 14 nights. It is compared to your sleep requirement, the quantity of sleep you need as established by your genes.

In practical terms, what does it mean? If you require 8 hours and 30 minutes of sleep each night but have only been receiving 7 hours of sleep per night, you have a significant amount of sleep debt.

A lack of sleep has far-reaching consequences on your mental and physical well-being, including your disposition and ability to get things done. Additionally, it makes you feel exhausted all day long, and a caffeine fix will not help if your sleep debt is too high. Caffeine may help give you a boost, but it simply covers up your exhaustion momentarily. If you are already sleep deprived and discover that coffee does not help, it might just be that your body is adjusting to the lack of rest. As a result, you might not feel active or awake even after you drank a cup of black coffee.

Caffeine-Related Sleep Loss

Caffeine-Related Sleep Loss

You can be feeling drowsy because you have a lot of sleep to catch up on. The problem might be exacerbated by caffeine. Ingesting caffeine too soon to bedtime may have serious consequences for sleep quality. You may not feel tired until much later because caffeine temporarily blocks adenosine receptors, so you may stay up much longer than your body usually wants you to. Insomnia is a vicious cycle; the less sleep you get, the more sleep debt you accumulate, leading to more fatigue and the temptation to drink more coffee to combat it.

More time passes than you may expect before the effects of caffeine wear off. It takes your body anywhere from 3 to 7 hours to metabolize half of the caffeine you ingested. Caffeine may have an effect for up to 12 hours, depending on how quickly your body processes it. This means that the effects of that latte you had at lunch might still linger at midnight, pushing back when you feel drowsy.

One study in Journal of Clinical Sleep Medicine concluded that a person who takes 400 mg of caffeine 0 – 6 hours before sleep is likely to suffer from sleep disruption. They are less likely to go in a state of deep sleep or get proper rest. This can have negative mental effects to the human body during the time they are awake.

Even after the effects of coffee have worn off, it might be difficult to get the amount of sleep you need. That is because you missed the optimal time for melatonin production. You will have a lot easier time falling asleep and staying asleep if you can squeeze your bedtime inside this timeframe. But if you skip it because you have been relying on coffee to stay up, you can find it more difficult to go to sleep later. The following day, even with coffee, you will feel even more exhausted due to the sleep debt you accumulated the night before. This is why you might feel sleepy even after drinking coffee.

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Coffee’s Diuretic Effect

Coffee's Diuretic Effect

As a diuretic, caffeine causes you to urinate more often. Caffeine may cause dehydration due to increased sweating, which may explain why some people report feeling sleepy after consuming it. Weariness is a typical sign of dehydration. Caffeine causes increased urination because it increases blood flow to the kidneys and blocks the reabsorption of salt, magnesium, and calcium.

There is some evidence that coffee may help get the bladder to contract and release its contents. However, this conclusion is not shared by other scientific communities regarding caffeine. One systematic review indicated that taking up to 400 milligrams of caffeine daily (about the equivalent of four cups of coffee) did not lead to dehydration.

However, excessive caffeine use might lead to loss of body fluids. In one study by BioMed Research International, subjects ingested 4 milligrams of caffeine for every pound of body weight. The volume of their urine rose by around 14 ounces in comparison to those who were given a placebo. If you have gone a few days without coffee, you may be more sensitive to its drying effects. This is why coffee makes you sleepy instead of wide awake.

However, the impact may not last forever. The use of caffeinated beverages such as coffee, tea, energy drinks, and soft drinks may also contribute to weariness since people who consume these beverages are less likely to drink water throughout the day.

Caffeine Tolerance

Development of Caffeine Tolerance

Although caffeine probably is not causing fatigue, it may no longer be providing the same level of alertness it once did. That is because tolerance may build up in the body, as confirmed in a study by researchers in Switzerland. This means that increasing doses will no longer provide the desired stimulating effects. Caffeine is used to conceal the symptoms of sleep debt or even simply general adenosine piling up during the day, but now you may start experiencing them if you do not increase your caffeine intake.

However, this is a dangerous slope. Caffeine is a common solution for people who are not getting enough sleep, but if you start drinking more of it to simulate the effects of coffee, there are going to be further problems. For example, you may find it difficult to fall asleep at night, fail to get enough sleep and wake up even more exhausted than before.

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Natural Energy Dip

Natural energy dip

Our energy levels change throughout the day as a result of our circadian rhythm, a 24-hour internal body clock. The ups and downs in our energy levels will occur regardless of whether or not we are sleep deprived. When it comes to energy, the afternoon is a particularly low point. Even those of us who are completely caught up in sleep may feel a little more sluggish and low on energy during this time. Those with significant sleep debt will feel it more acutely and for a longer period.

We do not see the connection between coffee and the situation at hand. Well, you may be feeling fatigued as a result of this drop in energy even if you have lately had a caffeinated drink.

Withdrawal Symptoms

Withdrawl of Coffee. Reason of why does coffee make you sleepy

Although it may seem contradictory to experience withdrawal symptoms while still taking coffee, studies have shown that this is possible. One research indicated that participants who regularly used 300 milligrams of caffeine had withdrawal symptoms when they decreased their intake to 200 milligrams or less.

Although 100 milligrams of caffeine may seem like a lot, it is around the amount of caffeine found in an average 8-ounce cup of coffee. If you are accustomed to drinking four cups of coffee daily, cutting down to three could leave you feeling exhausted, but it is the withdrawal symptoms, not the coffee, that are to blame. These symptoms may appear anywhere from 12 hours to a full day after your last cup of coffee, depending on your sensitivity to caffeine.

Without the stress hormone cortisol and the adrenaline that caffeine provides, you may find that you are less aware and awake than usual. The withdrawal from caffeine might cause the following symptoms:

  • Inability to focus
  • Mental Haze
  • Low mood
  • Headache
  • Fatigue

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Sugar Crash

Blood Sugar Crash

This is one of the most important reason why coffee makes you sleepy. Since most of us do not limit ourselves to black coffee, the sugar added to your beverage may be to blame for your fatigue rather than the caffeine. This is especially the case if you like to sweeten your coffee with sugar, artificial sweeteners, or flavored syrups, or if you often consume sugary soft drinks and energy beverages.

It probably isn’t the sugar in your coffee. You can get a sugar rush and then a sugar crash if you often drink coffee with a sugary breakfast or consume soft drinks with a lunch high in simple carbohydrates.

After consuming simple sweets, your blood sugar levels will surge, only to plummet a few hours later, leaving you feeling more exhausted than ever. For example, when your blood sugar suddenly drops, you could experience:

  • Fatigue
  • Headaches
  • Irritability
  • Hunger
  • Inability to focus

Asked by Reader: Why Does Coffee Make Me Dizzy in the Morning?

Coffee’s dizziness-inducing effects might be exacerbated by an empty stomach. Caffeine acts as an adrenaline precursor, causing the body to secrete the hormone shortly after ingestion. When this hormone is released, it gives you a boost of energy. This dizziness, however, may be caused by something else entirely: low blood sugar, especially if you drink coffee on an empty stomach. That is why it is crucial to eat something before drinking coffee. Although it is common for individuals to eat a healthy dinner with their coffee, this is not always the case.

How to Stay Alert After Drinking Coffee: Tips to Avoid Sleepiness

You can try out the following ideas prevent coffee from putting you to sleep.

Reducing Sleep Debt

If you want to feel and perform at your best every day and cut down on midday sleepiness, you should keep this under five hours. If you discover that you owe sleep a considerable sum of money, you might start making part of it back by

  • Resting and sleeping
  • Starting the day a bit later
  • Intent on getting some early shut-eye

Be Conscious of Your Caffeine Limit

If you are a coffee consumer who has trouble falling asleep and is fatigued throughout the day, your caffeine intake may be to fault. This does not mean you have to give up caffeine entirely; rather, you should just stop drinking it at the designated time each day. To provide your body enough time to metabolize caffeine before night, you should abstain from drinking caffeinated beverages after this time of day. Most people’s tolerance levels drop out after midday, however, night owls may be able to keep drinking coffee until 2 o’clock.

Since this depends on your circadian rhythm, the time will be different for each person and may shift somewhat from day to day. Keep in mind that it is not only coffee and soda that include caffeine; chocolate, particularly the darker varieties, does as well. It is also present, but in smaller amounts, in decaf coffee.

Reduce Caffeine Intake and Take Full Meal

The Cleveland Clinic reports that the effects of one cup of coffee might continue for up to 10 hours. However, dizziness might last for a while, perhaps up to a few hours. If you have been feeling lightheaded for more than a few hours, it is probably a good idea to rule out caffeine withdrawal as the cause.

To help your body adjust to the caffeine in coffee or energy drinks if you are experiencing withdrawal, sip on them carefully throughout the day. Even while cutting down on what you eat and drink can help you feel better, complete dinner and a few glasses of water cannot hurt.


Caffeine, found in beverages like coffee, soda, and energy drinks, is often used to help individuals feel more awake and alert first thing in the morning or during the day, particularly after a restless night. While getting a full night’s sleep every night is not always possible, it is necessary for avoiding caffeine crashes.

Caffeine is a short-term fix for fatigue and lack of energy, but it will not solve the underlying problem. Upon withdrawal, you might feel much more fatigued than previously. It is understandable if your reaction is to take in more of the stuff. The “coffee cycle” describes this routine, which may lead to habitual caffeine use.

Get some food before the first cup of coffee, or take a few glasses of water more than usual. However, if dizziness is making it hard for you to eat or drink, you should rest and replenish your fluids until the problem passes.

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