What else could a very low lithium in blood (0.15 nmol/l) mean besides possible bipolar disorder?

Lithium Level. Lithium is an essential mineral nutrient. It's not often measured specifically except when someone with bipolar disorder is taking pharmaceutical lithium -- which has a strict therapeutic range. A low serum lithium does not automatically mean bipolar disorder, but has been associated with increased risk for suicide, homicide, & some cases of autism. http://www.ncbi.nlm.nih.gov/pubmed/11838882.