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Why coffee doesn't wake you up: 6 unexpected reasons

Why coffee doesn't wake you up: 6 unexpected reasons Why coffee does not invigorate (illustration: Freepik)
Author: Daryna Vialko

Drinking coffee, especially in the morning, is widespread because it contains caffeine and other compounds that increase energy and improve mood. But even though coffee is a stimulant, sometimes drinking it doesn't have the desired effect - on the contrary, it makes you sleepy, as reported by the Sleep Foundation.

Why coffee doesn't help

Sleep deprivation

If you're constantly sleep deprived and not getting the recommended minimum hours of sleep per night, coffee, while it can be a pick-me-up, is not an adequate substitute for sleep.

When we don't get enough sleep, adenosine, a key chemical that helps make us sleepy, is released in greater amounts. However, coffee, while helping to increase alertness and reduce fatigue, blocks adenosine receptors, preventing the chemical from affecting sleep.

However, studies show that the body compensates for this effect by increasing sensitivity to adenosine. After the effects of coffee disappear, the increased sensitivity to adenosine contributes to drowsiness and muscle fatigue.

Using coffee to correct the effects of sleep deprivation can create a negative cycle: feeling more tired, you drink more coffee, but the coffee disrupts your sleep, leading to even more fatigue in the long run.

Caffeine tolerance

Instead of making you tired, it's possible that coffee doesn't make you as alert as it used to. Initially, caffeine consumption can improve mood and reaction time, as well as physical performance. However, those who consume caffeine regularly develop a tolerance to it.

As a result, consuming the same amount of caffeine over time will not have the same positive effects, and drinking more coffee to restore its positive effects may have negative consequences for your sleep.

In addition, regular caffeine consumption for as little as three days is enough to cause withdrawal symptoms when you stop drinking it, including increased fatigue.


Coffee is considered a diuretic, which means it can increase your need to urinate and lead to fluid loss. Mild dehydration can cause fatigue and can also reduce cognitive function, impair memory, and increase anxiety and tension.

In addition, coffee may be more likely to affect hydration in people who are not regular drinkers.

Changes in blood sugar levels

Drinking coffee in the morning can contribute to insulin resistance and negatively affect your body's ability to tolerate glucose.

This makes you more sensitive to the sugar or carbohydrates in your drink or breakfast and can cause your blood sugar to rise temporarily. High blood sugar is often associated with increased fatigue, especially in women.

Even if your blood sugar levels do not reach clinically high levels, you may experience increased fatigue due to changes in your sugar levels. In this case, it's best to make an appointment with your doctor, as sensitivity to changes in sugar levels may indicate certain health problems.

Caffeine metabolism

Metabolic rates vary - if your body metabolizes caffeine slowly, it may not make you feel energized as quickly as other people.

Conversely, if your metabolism is fast enough, caffeine may not affect you as much, or its effects may wear off faster, leading to a quicker feeling of sleepiness.

Many factors affect the rate of caffeine metabolism. Smoking cigarettes speeds up the metabolism of caffeine. Conversely, conditions such as pregnancy or liver disease can slow down the metabolism of caffeine.


Although more research is needed, scientists have found that genetics influence how a person responds to caffeine. Having certain genes may make you more susceptible to the negative effects of caffeine, such as anxiety or sleep disorders.

If caffeine consumption negatively affects your sleep, you may experience increased daytime fatigue.

Earlier, we wrote about which drinks are as invigorating as coffee.

Read also about which coffee is not harmful to the heart.

This material is for informational purposes only and should not be used for medical diagnosis or self-treatment. Our goal is to provide readers with accurate information about symptoms, causes, and methods of detecting diseases. RBС-Ukraine is not responsible for any diagnoses that readers may make based on materials from the resource. We do not recommend self-treatment and advise consulting a doctor in case of any health concerns.