How often you should have a medical checkup depends on your age, your health condition, and your medical insurance coverage. For most people, they try to avoid going to the doctor unless its an emergency. For women, when you're 50 you need to have a screening for breast cancer every 2 years. If you're a women, 21 or older, and have a cervix, you need a Pap test. Also, all pregnant women need to be tested for HIV. For men, they need a colonoscopy. If your family members have had colon cancer, you need to have a colonoscopy 10 years before the age at which they did. They also need an FOBT yearly after age 50. Both male and females need to have eye exams and vision screenings around age 18.