What does it mean when your stool is yellow and runny?

Lotta possibilities.: Without examination, I cannot give specific medical advice on your particular health. This is a perfect description of a liver problem (but only if the urine is dark brown !). There's lots of liver problems (infection, irritation, poisoning and many others). Other categories of causes. Not absorbing food (fat, protein, or carbohydrate). Mostly, not serious diet or viral causes. but need dr visit.