taking too much of a drug ("too high a dose") can cause sickness or even death. when a doctor says how much of a drug (the right dose) to take, only that amount should be taken. it is very important to keep taking the drug until the doctor says to stop because someone can feel better but still be sick. when a doctor says what drug to take, how much of it, and for how long, it is called a prescription. drugs may cause addiction. some drugs are illegal because they are very addictive. these drugs are really expensive, too. it can also be sold illegally from drug sellers which may cause serious results