Lithium is usually prescribed for mood-stabilizing purposes. Its possible side effects include nausea, diarrhea, sedation, polyuria (increased urination), increased thirst, tremors, hypothyroidism, and weight gain, to name a few. Long-term treatment with lithium or some other mood-stabilizer is usually the standard of care in the treatment of bipolar disorder. There are other mood stabilizers, Valproic acid (Depakote) being the most common. It is not without side effects (e.g. nausea, diarrhea, sedation, and weight gain), but is often better tolerated than lithium. Other mood stabilizing agents include Carbamazepine (Tegretol), Lamotrigine (Lamictal), and Gabapentin (Neurontin), to name a few. I urge you to discuss your concerns further with your treating physician/psychiatrist.