Dose and level don't correlate. For me it didn't even correlate in one person. I needed a higher level to feel good for the first 4 or 5 years I was on lithium and I took I think 1500 mg. Then I had toxicity #1 and it took a lot of trial and error to find my new right level and dose. I don't remember those numbers. I had toxicity #3 when things had been fine for a while and it was bad enough to land me in the medical hospital for a while. After that I took a lower dose (425 mg) and we tried to keep my level about .4. After a bad period with a suicide plan the hospital increased it so that my level would have been I think .8 or .9 but that didn't last very long because my level was all over the place and my pdoc put me back on the lower dose/.4 goal. But I got toxic again despite having been consistently that low and that was the end. We tried again out of desperation a few months ago but I needed a higher level than we know is safe for me so I had no response.

Lithium is weird. But it did work well for me when it wasn't making me toxic.