Caffeine comes from plant sources, and drinks like tea and coffee contain the substance naturally, but it is still a drug that acts physically on your body. Caffeine is best known as a way to wake up, stay awake and get fast energy. Those effects happen because of how the drug works on your nervous system. Your body processes and expels caffeine rather than allowing it to build up.

Time Frame

You feel caffeine's effects rapidly because it starts working on your nervous system in about five minutes and peaks in half an hour, the Centre for Addiction and Mental Health advises. Your body does not store the chemical, and its effects normally last for about four to six hours as it gets processes and eliminated. The effects wear off overnight, even if you consume large amounts of caffeine during the day. Heavy caffeine users often suffer from physical and mental withdrawal symptoms when they first wake up, although drinking coffee or tea or taking caffeine in some other form stops the symptoms.

Effects

Caffeine has several effects on your body before it leaves your system. Most people feel more alert after consuming it, are able to stay awake and are more mentally alert. Some people are more sensitive to those effects, especially physically smaller individuals. You get desensitized to the drug's effects if you consume it regularly in large amounts. For most people, that means more than 300 mg every day, according to MayoClinic.com. This requires you to use more caffeine to get the same energizing effects as you used to with a more modest amount.

Withdrawal

Caffeine withdrawal takes up to nine days to run its course, according to Johns Hopkins Medicine. Once caffeine is cleared out of a heavy user's body, flu-like symptoms, headache and other body soreness, crankiness and an upset stomach kick in. These effects reach their worst point within one to two days, lessening over the next seven to eight days until they disappear completely. You restart the cycle if you start using caffeine again. Minimize symptoms or prevent them completely by tapering off your caffeine consumption for several days until you are no longer consuming it at all. Use herbal teas and decaffeinated coffee to fulfill your taste for your usual caffeinated beverages.

Considerations

Coffee, tea, cola beverages and chocolate are commonly known as caffeine sources, and many energy drink makers add it to their products for its boost. The chemical also has lesser-known sources, like certain cold, flu and pain drugs. Read the ingredients list for over-the-counter pain pills and cold and flu remedies if you are controlling your caffeine intake. Caffeine-free options are available if you want to avoid the drug,