Exactly how caffeine impacts sleep

We have all heard that caffeine hinders sleep - but how does it actually do so? Read on to learn more about caffeine, how it may be impacting your sleep and some easy ways to adjust your intake to ensure a better night’s rest.

Is your daily coffee keeping you awake at night? Caffeine is found naturally in coffee, tea, and chocolate, but it’s also added to foods such as carbonated soft drinks and energy drinks and may even be found in some medications and supplements.

Caffeine has natural stimulant properties. Once consumed, it is rapidly absorbed and works by stimulating your central nervous system – its effects can be felt in as little as 15 minutes. It is this stimulation, or excitement of the nervous system that can have numerous effects throughout your body. Caffeine increases wakefulness and can make you feel more mentally alert, which is exactly why you may reach for a cup of coffee to help you get through those early mornings! But caffeine increases alertness by interfering with a chemical process that regulates your sleep-wake cycle. It blocks the sleep-inducing chemical adenosine from binding to receptors in your brain, which can prevent it from doing its job to induce sleepiness at bedtime.

How to tell if your caffeine consumption is impacting your sleep

Do you have trouble falling asleep? Or perhaps you are not sleeping for as long as you would like to each night? Caffeine could be a contributing culprit. Caffeine has an average half-life of five hours; this means that it takes approximately five hours for half of the caffeine you consumed to be eliminated from your body – the remaining caffeine is present for several hours longer and can continue to exert effects on your body.

In addition to increasing alertness (not what you want at bedtime!), caffeine’s stimulating effects can cause rapid heart rate, difficulty sleeping, irritability and nervousness. Even in doses as low as you would find in one cup of coffee, caffeine may increase the time it takes to fall asleep, reduce sleep quality, and reduce the length of time you are able to sleep.

If you consume caffeine too late in the day, or are naturally sensitive to its effects, it could impact your sleep. In this case, you may want to consider how much caffeine you’re getting each day and the timing of when you’re consuming it. The good news is, you don’t have to quit caffeine altogether, but making some small adjustments to your intake may pay off with a better night’s sleep.

Here are some tips and tricks to prevent caffeine from affecting your sleep or reduce your dependence on caffeine in general:

  • Check your diet for all sources of caffeine – remember that it’s not just your daily coffee that may be contributing to your overall intake. Caffeine is found naturally in coffee, tea, cocoa and chocolate-containing foods, and plants such as kola nut, guarana (used in energy drinks, soft drinks, and some herbal teas), and yerba mate (a South American herb used to make tea). Caffeine may also be added to carbonated soft drinks, energy drinks, supplements, and some headache and cold medications. If you’re unsure if a product contains caffeine, you’ll be able to find this information in the ingredients list on the product label.
  • Moderation is key. For adults 19 years of age and older, 400 milligrams (mg) of caffeine is considered a safe amount to consume daily. If you are planning to become pregnant or are pregnant or breastfeeding, the general recommendation is to limit your intake to 300 mg of caffeine daily. Here are some common caffeine-containing beverages and the average amount of caffeine they contain:

FoodServing SizeCaffeine (mg)
Coffee, brewed1 cup (250 ml/8 oz)80-179
Tea, leaf or bag, black or flavoured black1 cup (250 ml/8 oz)43-50
Cola355 ml (1 can)37-38
Energy drink1 cup (250 ml/8 oz)80-97

  • Enjoy more non-caffeinated beverages, such as water or flavoured herbal tea, served hot or over ice.
  • Avoid consuming caffeine after 12:00 pm. Switch to non-caffeinated beverages in the afternoon and evening.
  • Gradually reduce the amount of coffee you drink. Some simple ways to do this are by drinking half caffeinated and half decaf coffee; or if you typically have three cups of coffee a day, have two cups of regular coffee and one cup of decaf coffee. Continue to reduce your intake gradually over a period of at least several days.
  • Avoid going cold turkey. If you suddenly stop consuming caffeine, you may experience headaches, fatigue or drowsiness, impaired concentration, and moodiness or irritability, so it’s a safe bet to wean yourself off slowly to mitigate any negative effects.

Coffee and other caffeine-containing beverages and foods can be enjoyed as part of a healthy lifestyle. But if you are having trouble sleeping, you may want to take a closer look at whether you’re consuming too much caffeine or having it too late in the day. By making some simple adjustments, you may find that you’re able to hit the pillow easier and get a more restful night’s sleep.



Food Sources of Caffeine. Dietitians of Canada, PEN® The Global Resource for Nutrition Practice. 2016, April 28.

Glade MJ. Caffeine-Not just a stimulant. Nutrition. 2010 Oct;26(10):932-8. Abstract available: https://www.ncbi.nlm.nih.gov/pubmed/20888549

Heckman MA, Weil J, Gonzalez de Mejia E. Caffeine (1, 3, 7-trimethylxanthine) in foods: a comprehensive review on consumption, functionality, safety, and regulatory matters. J Food Sci. 2010;75(3):R77-87. Abstract available: https://www.ncbi.nlm.nih.gov/pubmed/20492310

Ker K, Edwards PJ, Felix LM, Blackhall K, Roberts I. Caffeine for the prevention of injuries and errors in shift workers. Cochrane Database System Rev. 2010,Issue 5. Art. No.: CD008508. Abstract available: https://www.ncbi.nlm.nih.gov/pubmed/20464765

Reissig CJ, Strain EC, Griffiths RR. Caffeinated energy drinks--a growing problem. Drug Alcohol Depend. 2009 Jan 1;99(1-3):1-10. Abstract available: https://www.ncbi.nlm.nih.gov/pubmed/18809264

Roehrs T, Roth T. Caffeine: sleep and daytime sleepiness. Sleep Med Rev. 2008 Apr;12(2):153-62. Epub 2007 Oct 18. Abstract available: