I have high bilirubin. i'm 23 years old. what does this lead to and how can i prevent it?

Maybe nothing: Many people have elevated bilirubin levels. If there are no other liver abnormalities, it is called gilbert's syndrome. People with this may turn yellow if they get sick. Otherwise, it is completely benign. Have your doctor or a liver specialist check it out.

How high?: If it is less than 5 mg/dL and has not changed over the months, you probably have a benign disorder, Gilbert disease/syndrome. Visit this site for more info: https://www.mayoclinic.org/diseases-conditions/gilberts-syndrome/symptoms-causes/syc-20372811

Gilbert's syndrome: Gilbert's syndrome, also known as constitutional hyperbilirubinemia, is a congenital condition causing elevation of the indirect bilirubin fraction, but the direct fraction is normal. No symptoms are usual in this benign lifelong condition although mild jaundice may be seen during certain conditions like exertion. No treatment is needed. Check with your physician to see if you have this syndrome.