How often is diabetes insipidus from lithium reversible?

Early = better: I can't tell you how often, but I can strongly urge you to see your provider ASAP to stop taking lithium and if this is a fairly new problem, it is more likely to reverse, but it can take time. The damage done is to the kidney - be sure to stay well hydrated and make an appointment. I hope you've caught it in time - good thinking to ask! Best wishes for a good result!