MBD is a curable bone disease, but if you leave it untreated then it can be fatal. It depends on the lizard and the severity of their condition as to how quickly the disease will kill them if they do not receive any treatment. Once your bearded dragon has received the right medical attention and has started treatment, their symptoms will gradually begin to improve as their bones become healthier. The best cure is to prevent the disease from developing in the first place by ensuring that you provide the right living conditions for your bearded dragon.