Background: Lithium is a first-line treatment for bipolar disorder in all phases, also indicated as add-on drug for unipolar depression and suicide prevention. This study encompasses a broad critical review on the safety and tolerability of lithium for mood disorders. Methods: A computerized search for English written human studies was made in MEDLINE, using the keywords "lithium" and "mood disorders", starting from July 1993 through July 2013 (n = 416). This initial search aimed to select clinical trials, prospective data, and controlled design studies of lithium treatment for mood disorders reporting adverse effects (n = 36). The final selection yielded 91 studies. Results: The most common general side effects in patients on lithium treatment were thirst, frequent urination, dry mouth, weight gain, fatigue and cognitive complaints. Lithium users showed a high prevalence of hypothyroidism, hyperparathyroidism, and decrease in urinary concentration ability. Reduction of glomerular filtration rate in patients using lithium was also observed, but in a lesser extent. The evidence of teratogenicity associated with lithium use is not well established. Anti-inflammatory non-steroidal drugs, thiazide diuretics, angiotensin-converting enzyme inhibitors, and alprazolam may increase serum lithium and the consequent risk for intoxication. Discussion: Short-term lithium treatment is associated with mild side effects. Medium and long-term lithium treatment, however, might have effects on target organs which may be prevented by periodical monitoring. Overall, lithium is still a safe option for the treatment of mood disorders.