Substance abuse includes the overuse or abuse of alcohol or illegal drugs as well as the misuse or overuse of prescription medications. Fatigue often is related to substance abuse.

You have an alcohol problem if your use of alcohol interferes with your health or daily living. The overuse or abuse of alcohol can cause fatigue, as well as many other problems.

Drug use includes the illegal use of marijuana, cocaine, heroin, or other "street drugs," and the abuse of legal prescription and nonprescription drugs. Some people turn to drugs to get "high" or to deal with stress and emotional problems. Drug use can cause fatigue, as well as many other problems.

Withdrawal from alcohol or drugs also may cause fatigue.

Overuse of caffeine can cause sleep problems that may lead to fatigue. Decrease your use of caffeine if you think it may be causing your fatigue.

If you think alcohol abuse, illegal drug use, or withdrawal is causing your fatigue, and you are unable to stop using the drug, call your doctor.