How do u know if ur rabbit hairballs?

How do u know if a rabbit has a hairball? It worrys me cuz I never know if my rabbit has one and all the books I read don't really tell me please help

If bunny is pooping and peeing normally, not to worry! If they have a hairball in their gut, usually their digestive system stops working and this can result in an emergency visit to the vet. If you feed bunny mostly hay 24/7 and only the recommended amount of pellets (usually 1/4 c or so, depending on the weight of bunny), his digestive system should be fine. Brush your rabbit when he is having a heavy shed with a soft brush or comb to remove excess hair. This will remove loose fur and make him ingest less of it. Also make sure bunny has plenty of fresh water to drink every day - water out of a bowl is best if replaced daily, since water bottles require a lot of effort for bunny to get enough water. Don't give bunny any anti-hairball treatments meant for cats or dogs. These are poisonous for rabbits.