Medical doctors treat patients by finding out what is wrong with them, known as a diagnosis. They ask questions about the patient's symptoms. These might include fever or pain. They may ask about past illnesses or family members who have been sick. They will then examine the patient. They look at different parts of the body, listen to the heart and lungs with a stethoscope. Sometimes they may need to collect a sample of blood, use an x-ray machine, or use other tools. When they have gathered enough information, a doctor can make a diagnosis and then plan a treatment. Often they prescribe drugs.