1.25mg/day is well enough within the normal human range that I wouldn't worry about taking that rather than 1.25mg. See Schrauzer's paper below.

FYI, this is the section on lithium that ended up being excised from my paper.

Lithium is not typically considered an essential dietary mineral, but evidence is emerging that minute amounts of lithium benefit physical health and mental well-being. Lithium is widely regarded as potentially toxic, but this is true only of the macro amounts prescribed in mental health treatment. Recommended supplemental levels of lithium are about 3 orders of magnitude lower than commonly prescribed dosages.

Micro doses of lithium in the water very significantly reduce suicide in populations, even when adjusted for various confounding factors, including studies in Austria [BJP Lithium in drinking water and suicide mortality] and Japan [BJP Lithium levels in drinking water and risk of suicide]. Also shown to reduce criminality along with suicide. [http://www.ncbi.nlm.nih.gov/pubmed/1699579 Lithium in drinking water and the incidences of crimes, suicides, and arrests related to drug addictions.]

1000 ug/day has been proposed as a provisional safe upper limit for lithium microdosing by Schrauzer [Lithium: Occurrence, Dietary Intakes, Nutritional Essentiality http://www.jacn.org/content/21/1/14.full], claiming that the evidence is such to establish lithium as an essential dietary element. This seems as true as any claim made in nutritional research and I recommend supplementing low dose lithium. Short of a prescribing practitioner, microdose lithium can be had in ConcenTrace trace mineral supplement, with 400ug/dose.