How Much Caffeine Negatively Impacts Sleep?

Millions of people around the world rely on caffeine for energy (up to 90% of Americans, according to some estimates). But what does this commonly consumed stimulant mean for sleep?

What is caffeine?

In its purest form, caffeine is a bitter substance found in coffee beans, tea leaves, kola nuts (what gives cola soft drinks their flavor), and cacao pods (yep, chocolate). Synthetic caffeine is often added to pain relievers and cold medications, foods, and energy drinks. The majority of people get their caffeine from beverages – for example, the 400 million cups of coffee consumed in America each day. While most people who drink caffeine do it in the morning (65% of coffee drinkers have a cup with breakfast), the trick to limiting caffeine’s effects on sleep is to curtail it in the afternoon.

Want to see how caffeine can influence your unique sleep? Download the SleepScore app to log your daily caffeine intake and track your sleep to see how you sleep that night. Try it for free!


How Does Caffeine Work?

Caffeine stimulates your body’s central nervous system, increasing alertness and reducing fatigue. Once ingested, caffeine takes effect within 15 to 20 minutes, and half of that caffeine can remain in your system for six or more hours. This is what experts describe as caffeine’s half-life, or the amount of time it takes caffeine to work its way out of your system. To put it in context, if you drink 200mg of caffeine at noon, you’ll still have 100mg in your system at 6pm. Of course, how quickly you metabolize caffeine depends on your body size and tolerance level. But those afternoon espressos might be the reason you’re still staring at the ceiling come 1am.

Caffeine also stimulates the production of adrenaline, an alertness-boosting hormone that is linked to your body’s fight or flight response. An increase in adrenaline raises your heart rate, increases your breathing, and brings on a state of increased vigilance. Caffeine also blocks the effectiveness of adenosine, a chemical that helps to bring on drowsiness and regulate your sleep-wake cycle. Additionally, caffeine alters sleep architecture, the overall nightly distribution of sleep among the different sleep stages. Over-caffeinating can reduce time spent in deep sleep, the phase that is critical for physical rejuvenation.

You can track your sleep and see how much caffeine is the right amount for you by downloading the SleepScore app.

SleepScore app at Google Play Store

SleepScore Sleep Tracker App


How can you cut back?

Like any drug, your body can become addicted to caffeine. If you think your consumption might be interfering with your sleep, it’s best to wean yourself off gradually. Going cold turkey might leave you with headaches, irritability, and fatigue. Instead, start the day with the most highly caffeinated beverage and gradually taper down from there. Switch to a half-regular, half-decaf cup of coffee, or to tea, before forgoing caffeine altogether for the remainder of the day. You might also consider a caffeine alternative to help ease the transition. A general guideline for ensuring that caffeine doesn’t interfere with sleep is to cut yourself off at 2pm.

Looking for a delicious caffeine-free alternative that still reminds you of your afternoon cup-of-joe? Check out these tasty blends in our SleepShop!

Another great strategy is to monitor how much caffeine you’re actually drinking each day. Depending on the drink, the caffeine levels can vary widely.

  • An 8-ounce cup of coffee contains between 95-200mg; a 12-ounce can of soda, 35-45mg
  • An 8-ounce energy drink, 75-100mg
  • An 8-ounce cup of tea can have anywhere between 14 and 60mg, depending on the type of tea.

Experts agree that consuming up to 400mg of caffeine per day is not harmful for most people. Depending on what you order from your favorite barista or coffee pot at the office, you might hit that limit with only two drinks.

The link between caffeine and sleep may seem logical, but many people are unaware of their own habits. Being mindful of how much caffeine you consume – and when – is key to ensuring that it doesn’t interfere with getting the sleep you need.

“Coffee by the Numbers.” Harvard T.H. Chan School of Public Health

“America’s Coffee Obsession: Fun Facts That Prove We’re Hooked.” Kitchen Daily.

“Caffeine.” Medline Plus.

“About Caffeine” Villanova University
“Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed”. Journal of Clinical Sleep

“Caffeine and Sleep”. National Sleep Foundation.
“Effect of Caffeine on Sleep”. US National Library of Medicine, National Institutes of

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