Effects - these help to eliminate fluid from the body. Athletes may use these substances in an attempt to lose weight if competing in sports with a weight category, or to increase the rate that urine is produced and eliminated to help dilute the urine, which, in turn, would make it difficult to detect other substances. Dangers - the misuse of diuretics can cause dehydration, faintness, dizziness, muscle cramps, headaches, nausea, abnormal heart rhythms. Severe dehydration can cause the kidneys and heart to stop working, which could be fatal.