My brother is on lithium 900 mg per day. Different labs have different therapeutic goals mentioned in their report. For example when we go to lalpath lab it says normal range is 0.4-1.2 mmol/L and each time his lithium level are 3.6 or 3.8 . And when we go to other labs, they say good range 0.6-1.2 mmol/l and each time his lithium level are around 0.52-0.56 mmol/L. I'm confused if his lithium levels are 0.35 or 0.55 .