If you don't feel well, you may worry that you have COVID-19. The only way to know for sure is to take a test. At-home tests can tell whether you have the virus right now. More specialized antibody ...

A complement C4 (also known as a complement component 4, or simply C4) is a test to measure the level of C4 proteins you have in your blood. These proteins play a role in how your immune system ...

Jay N. Yepuri, MD, MS, FACG, is a board-certified gastroenterologist and member of the Digestive Health Associates of Texas Board of Directors and Executive Committee. A liver function test checks how ...

Matt Webber is an experienced personal finance writer, researcher, and editor. He has published widely on personal finance, marketing, and the impact of technology on contemporary arts and culture.