How Does a Caffeine Nap Work?

Caffeine and Sleep Both Impact Adenosine, Decrease Sleepiness


Perhaps you have heard of something called a “caffeine nap” or a “coffee nap”. It may be touted as a way to maximize the effectiveness of both a serving of caffeine and a nap to improve daytime sleepiness. How might this work? When is the best time to attempt it during the day? How much caffeine and how long of nap is optimal? Learn more about caffeine naps and whether they might be just what you need to feel better during the late day.

What Is a Caffeine Nap?

A caffeine nap is a short period of sleep that occurs during the day immediately following the consumption of caffeine. The nap should be kept to 15-20 minutes and it may be important to set an alarm to prevent oversleeping. Typically one or two servings of caffeine are enjoyed, and most studies showing a benefit have tested 150 to 200 mg of caffeine. (For reference, a cup of brewed coffee has 163 mg of caffeine.) The source of this caffeine doesn’t matter with many options existing, including: coffee, tea, soda pop, energy drinks, chocolate, caffeine pills, etc. Depending on what you consume, the amount of caffeine may vary and how much you routinely drink (or eat) may also affect your sensitivity to it.

How Does a Caffeine Nap Work?

Our desire for sleep is dependent on two processes: homeostatic sleep drive and the circadian alerting signal. Sleep drive refers to the fact that the longer you stay awake, the sleepier you will become.

This is due to the accumulation of a chemical in the brain called adenosine. Adenosine is a normal byproduct of metabolism. Cells in the body use adenosine triphosphate (ATP) as their primary source of energy. The leftover component of this energy use is the adenosine. The longer we are awake, the more energy we use and the more adenosine accumulates within the brain.

This is one of the primary substances that make us feel sleepy.

Sleep is, at least in part, a process of clearing away the accumulated adenosine. By morning, after a good night of sleep, the levels are lowered and then start increasing with prolonged wakefulness. If you only get 4 hours of sleep one night, you wake up feeling sleepy because you didn’t have sufficient time to clear out the adenosine. It is important to recognize that even short periods of sleep may effectively reduce the adenosine levels. Therefore, a nap may reduce sleepiness and increase alertness.

When caffeine is coupled with a nap, these effects are enhanced. Caffeine independently works to block adenosine, the signal for sleepiness. This is how it acts as a stimulant and works to make us feel more awake, even if we don’t sleep. As a result, a caffeine nap pairs two interventions that are known to reduce sleepiness. Research demonstrates the combination is more effective than either by itself in improving measures of alertness.

When Should You Take a Caffeine Nap?

In general, you should consider taking a caffeine nap when you are feeling extra sleepy during the day. For most people this may correspond to a natural dip in the circadian alerting signal that occurs in the afternoon, often between 1 PM and 3 PM. Incidentally, this is why entire societies observe siesta time in the early afternoon (which is often the hottest part of the day for them).

To avoid insomnia, it’s probably best to avoid taking a caffeine nap later in the day or near bedtime. Caffeine is metabolized by the liver, and about half of it will be eliminated in 5-6 hours, so you may want to avoid it beyond the late afternoon if you are sensitive or prone to insomnia.

Other Ways to Avoid Daytime Sleepiness

If you are excessively sleepy during the day, it is most likely due to inadequate sleep quality or quantity. Sleep deprivation will often occur for adults when fewer than 7-8 hours of sleep are routinely obtained. Try to get adequate hours of sleep at night, keep your sleep schedule regular, and get 15-30 minutes of morning sunlight upon awakening. There are also other ways you can improve your sleep.

In addition, sleep disorders such as obstructive sleep apnea may undermine the quality of sleep at night. It leads to frequent arousals from sleep to resume breathing that can lead to unrefreshing sleep, excessive daytime sleepiness, and frequent naps. If you experience snoring, getting up to urinate at night, and teeth grinding, you should seek further evaluation.

Remember that caffeine is no substitute for sleep. Though it may mask the symptoms of sleepiness, the effects are temporary. Never drive if you are feeling too drowsy. If you are routinely feeling too sleepy during the day, see a sleep doctor to discover how your sleep can be improved.


Bonnet, MH. “The use of prophylactic naps and caffeine to maintain performance during a continuous operation.” Ergonomics. 1994 Jun;37(6):1009-1020.

"Caffeine Content of Drinks." Caffeineinformer. Last accessed: February 28, 2015.

Hayashi, M et al. “The alerting effects of caffeine, bright light and face washing after a short daytime nap.” Clinical Neurophysiology. 2003 Dec;114(12):2268-2278.

Horne, JA et al. “Counteracting driver sleepiness: effects of napping, caffeine, and placebo.” Psychophysiology. 1996 May;33(3):306-309.

Reyner, LA et al. “Suppression of sleepiness in drivers: combination of caffeine with a short nap.” Psychophysiology. 1997 Nov;34(6):721-725.

Continue Reading