Caffeine is the most widely consumed stimulant in the world. That being said, it does not affect everyone in the same way.
Some people, for example, can drink multiple cups during the day and experience few effects. Others may experience adverse effects after drinking a single cup of coffee.
According to the Food and Drug Administration (FDA), an average 8 ounce (oz) cup of coffee contains around 80–100 milligrams (mg) of caffeine.
In this article, we look at why coffee makes some people feel tired. We also discuss other potential effects of coffee and daily intake recommendations.