A PSA test is a blood test. It measures PSA, a protein made by the prostate. A high PSA level may be a sign of prostate cancer. But many other things can also raise PSA levels. Screening means having tests that look for cancer before you have symptoms. A screening test only tells you whether you might have cancer. It does not diagnose cancer on its own. If a screening test looks unusual, you will need more tests. These may include a digital rectal exam, where a doctor feels the prostate for anything unusual, or a biopsy. A biopsy is the only way to truly diagnose prostate cancer. Prostate cancer often grows slowly and may never cause health problems. Some people live long lives with prostate cancer and never notice it. In other cases, it can spread and become serious. The goal of screening is to find cancers more likely to spread, so they can be treated early. Which tests are right depends on age, family history, and other risk factors. Because of this, screening is a personal decision made together with your care team.