What should I do if a 'Cartridge is low' or 'Cartridge is very low' message appears?

The 'Cartridge is low' or 'Cartridge is very low' message will display on the printer control panel or EWS when toner is running low. The manual addresses this issue in the Solve Problems section. You can continue printing until print quality becomes unacceptable, at which point the cartridge should be replaced. (Page 129)