This is the info that's in my drug book:

Do you have a sodium deficit?
A sodium deficit causes more lithium to be reabsorbed and increases the risk of lithiium toxicity.

Toxic manifestations of lithium include nystagmus, tremors, oliguria, confusion, impaired consciousness, visual or tactile hallucinations, choreiform movements, convulsions, coma, and death.

Adverse effects with lithium:
Common : metallic taste, hand tremors, nausea, polyuria, polydipsia, diarrhea, muscular weakness, fatigue, edema, weight gain. These usually subside during the first few weeks of drug therapy.
Severe adverse effects: more severe nausea and diarrhea, vomiting, ataxia, incoordination, dizziness, slurred speech, blurred vision, tinnitus, muscle twitching and tremors, increased muscle tone.

Nausea may be decreased by giving lithium with meals.