Lower left abdominal pain can have many causes, ranging from minor to serious, says Andrew Boxer, M.D., gastroenterologist of ...

Sleeping with a pillow between our knees, too, feels best. So why is the left side the best? One night, I had horrible heartburn, which rarely happens, so I immediately Googled to find out what to do.

Different headache types can cause pain on the left side of the head. The pain usually isn’t cause for worry. But if the pain is intense or doesn’t go away, there may be a more serious cause.