What blood tests detect a bad liver? when would a doctor worry about this in general blood work?

Depends : There are different test for different types of disorders. Screening tests include ALT, AST, Alkaline phosphatase, and Bilirubin. An acute hepatitis panel and a so called liver panel may be used. Have a healthy diet, exercise 30 minutes/day, drink plenty of water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. For nutrition: http://www.choosemyplate