The Effects of Caffeine on Sleep

Caffeine is a stimulant that energizes the body, boosts mental alertness, and prevents drowsiness temporarily. Coffee, tea, energy drinks, and sports drinks are just a few of the many products that contain caffeine. These drinks are typically consumed to boost endurance or mental alertness while engaged in rigorous activities.

The Effects of Caffeine on the Human Body

As a stimulant, caffeine affects the body within minutes of consumption. Within 15 minutes of drinking a caffeinated drink, caffeine is absorbed into the bloodstream, peaking in 60 minutes or less. The effects could last for 3 to 5 hours, depending on the amount of caffeine consumed. Sometimes, the effects could last for 8 to 14 hours. Caffeine’s effects take a while to wear off because the body is unable to get rid of the chemical completely even after urinating several times.

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Moderate consumption of caffeine – about 250 mg or equivalent to 3 cups of coffee daily – will not pose any danger to the health. However, too much of a good thing can be bad for the health too. Caffeine is known to disrupt sleep and enhance the symptoms of insomnia. In today’s post, we are listing down the effects of caffeine on sleep.

Effects of Caffeine on Sleep

Sleep Disturbance

Consuming one cup too many of coffee will affect your sleep cycle at night. Excessive caffeine intake causes mild sleep disturbance at night, a condition that makes it difficult to fall asleep at night or makes it hard to stay asleep temporarily. Mild sleep disturbance leads to sleep deprivation and sleep deprivation causes daytime sleepiness, drowsiness, and decreased mental alertness throughout the day.

The fact is, caffeine stays in the system for a long time and taking more caffeine within its peak period will extend its effects. To prevent sleep disturbances, do not take caffeinated drinks six hours before going to bed. If you can, drink caffeinated drinks in the mornings, not late in the afternoon.


Insomnia is a sleep disorder that makes it hard for one to fall or stay asleep at night. If you suffer from this disorder, drinking caffeinated drinks is not a good idea at all. Consuming caffeinated drinks, especially during the late afternoon or early evening, will over-stimulate the central nervous system, putting you in a wakeful state for longer. This unnatural state of wakefulness has long-term effects on your sleep cycle, leading to sleepless nights. Caffeine-induced insomnia will lead to daytime sleepiness, irritability, drowsiness, decreased mental alertness, and difficulty concentrating.

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Caffeine boosts cardiovascular activities, increasing blood pressure and heart rate. When the circulatory system is working extra hard to pump blood, the renal system becomes inundated with a higher-than-normal volume of blood to filter out. When this happens, the renal system processes more waste, leading to frequent urination. According to a study by the National Institutes of Health, adult coffee drinkers release 2.5 liters more of urine per day, leading to dehydration. In addition, frequent urination will disrupt sleep too.

Unfortunately, caffeine also affects the ability of the bladder to hold urine. The chemical relaxes the detrusor muscles, causing the bladder to feel fuller more frequently, leading to more trips to the bathroom all day and all night long.

Fight or Flight Response

Consuming too much caffeine triggers the body’s “fight or flight” response, which essentially involves flooding the system with adrenaline in case of an emergency. This would’ve been useful back in the prehistoric age when humans have to defend themselves against bigger predators but not at the present. When the body’s fight or flight response is triggered, it’s hard to fall right back to sleep, leading to sleep deprivation, palpitation, and daytime sleepiness.