How long does take to lithium leave the body and have normal blood levels for a person taking 1200 lithobid (lithium carbonate) and changing med?

Lithium. Lithium has a half life that depends on a few factors, to include the amount of time it is taken, age of the patient, and how well the kidneys are working. On average, it is about a day, so you would expect to be completely clear of the medication 5 days after ceasing. Measurable blood levels will likely be normal within a couple days, however.