You get headaches
A moderate amount of caffeine can help relieve a headache and make you feel better, by helping pain-relief medications work more effectively, according to the Cleveland Clinic. That’s why you’ll find caffeine as an ingredient in many over-the-counter headache drugs. However, if you drink too much coffee for a sustained amount of time (getting an daily excess of 500 mg of caffeine, or the equivalent of five cups of coffee) and you can go through caffeine withdrawal. The symptoms include headaches and fatigue, found Johns Hopkins researchers. Slowly decrease your caffeine intake—and look at all the possible sources in your diet, including coffee, headache drugs, tea, soda, and energy drinks.