Experts Explain Why Caffeine Makes You Tired

And how to avoid a coffee crash.

Experts explain why your caffeine might actually be making you tired.
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If you rely on your morning coffee to get you energized for the day, then feeling tired after your daily dose of caffeine is probably the last thing you’d expect. But, unfortunately, it can happen (sorry, coffee lovers) — hence why some people are left wondering: “Why does caffeine make me tired?” Turns out there are several reasons behind the seemingly contradictory side effect that, once you learn them, can help you prevent it.

Caffeine is actually a stimulant, so it boosts your energy levels and increases your alertness by kicking your central nervous system into high gear, signaling your brain to feel awake and alert — hence the confusion when the opposite happens. You most commonly get it through coffee, but various kinds of tea and chocolate are other natural sources of caffeine you can consume.

But there are a number of reasons your caffeine hit can go awry, says Lindsay Kluge, LDN, a clinical herbalist and licensed nutritionist at herbal tea company Pukka. From how you’re consuming caffeine to your stress levels, experts explain the reasons why caffeine makes you tired to help you pinpoint why your brew isn’t having the desired effect.

1. It Blocks Adenosine

You have a chemical in your body called adenosine, which helps regulate your circadian rhythm, says Kluge. During the day, adenosine levels rise to keep you awake, and when you sleep, they drop. Caffeine makes you feel alert by temporarily blocking adenosine receptors in your brain to keep those levels high, says Kluge. But if you consume caffeine in excess (which studies suggest is anything over about 400 milligrams a day), you can crash as the caffeine wears off and adenosine levels change.

“Once the effects of caffeine go away, those adenosine receptors are now open to be filled with all our accumulated adenosine, which slow down brain molecules to help us sleep,” she tells Bustle. “Thus we can feel extra sleepy after we metabolize that hit of caffeine.”

2. The Added Sugars Drain Your Energy

Sometimes it’s not the caffeine that’s making you tired, but the sugar in the caffeinated drink you’re chugging. Added sugars in your coffee concoction can cause a spike in your insulin levels, which lowers your blood sugar and can make you feel tired, says Kent Yoshimura, co-founder and CEO of supplement brand Neuro. His solution? Try to cut back on the sugar or balance out your sweet drink with a protein-rich snack like nuts or eggs, which studies show can help regulate blood sugar levels.

3. It Increases Stress Hormone Levels

Caffeine can elevate your levels of a stress hormone called cortisol, says Yoshimura. And excess cortisol can have side effects of its own, including dizziness, trouble sleeping, and — you guessed it — fatigue. And this can further spike cortisol levels that may already be high due to other stressors, which can add to your feeling sluggish.

How To Deal

The most effective method to avoid caffeine-related crashes? It’s all about balance, says Yoshimura. “The best way to counteract caffeine fatigue is to use it responsibly,” he tells Bustle.

If you often feel tired after consuming caffeine, Kluge recommends eliminating it altogether. But if that’s not in the cards, minimizing your intake can help you maintain good energy levels all day long. She suggests weaning down to one cup of coffee in the morning (that’s about 95 milligrams of caffeine on average), swapping your coffee for lower- or no-caffeine alternatives like tea or chicory root coffee, and avoiding caffeine starting about six hours before bedtime.

Studies referenced:

Hou, Y. (2018). A Randomized Controlled Trial to Compare the Effect of Peanuts and Almonds on the Cardio-Metabolic and Inflammatory Parameters in Patients with Type 2 Diabetes Mellitus. Nutrients, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6267433/

Lazarus, M. (2019). Gating and the Need for Sleep: Dissociable Effects of Adenosine A1 and A2A Receptors. Frontiers in Neuroscience, https://www.frontiersin.org/articles/10.3389/fnins.2019.00740/full

Lovallo, W. (2005). Caffeine Stimulation of Cortisol Secretion Across the Waking Hours in Relation to Caffeine Intake Levels. Psychosomatic Medicine, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2257922/

Mitchell, D. (2014). Beverage caffeine intakes in the U.S. Food and Chemical Toxicology, https://www.sciencedirect.com/science/article/pii/S0278691513007175?via%3Dihub

Nehlig, A. (1992). Caffeine and the central nervous system: mechanisms of action, biochemical, metabolic and psychostimulant effects. Brain Research Reviews, https://pubmed.ncbi.nlm.nih.gov/1356551/

Porkka-Heiskanen, T. (1999). Adenosine in sleep and wakefulness. Annals of Internal Medicine, https://pubmed.ncbi.nlm.nih.gov/10344585/

Ribeiro, J. (2010). Caffeine and adenosine. Journal of Alzheimer's Disease, https://pubmed.ncbi.nlm.nih.gov/20164566/

Wikoff, D. (2017). Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children. Food and Chemical Toxicology, https://pubmed.ncbi.nlm.nih.gov/28438661/


Lindsay Kluge, MS, CNS, LDN, clinical herbalist and licensed nutritionist at herbal tea company Pukka

Kent Yoshimura, co-founder and CEO of supplement brand Neuro