The importance of knowing your cholesterol numbers cannot be overestimated, this is what cholesterol testing is all about. For someone with normal numbers and no additional predictive factors pointing to a danger of high cholesterol, the few tests advised by the doctor should be sufficient. For someone 20 years or older, a test every 5 years is the suggested number - until the results start showing high cholesterol. If you have high numbers and a condition that adds to the problem like diabetes or the need to take medication that raises cholesterol, more frequent tests are advised.