Most of the cost of your hospitalisation will be paid by your health insurance provider. Your hospital invoice will clearly state which costs will be charged to your health insurance provider and which costs you will need to pay yourself.
If necessary, ask your health insurance provider in advance which costs they will refund.
If you have hospital insurance, ask your insurer which costs will be refunded prior to your stay, if necessary. More detail is provided on your policy document.
If you do not have any valid Belgian health insurance, you will need to pay the entire invoice yourself.