Before starting a patient on lithium therapy, the doctor should order tests for kidney function and thyroid. Lithium is excreted from the body via the kidneys, and can cause changes to both kidney and thyroid function, so it is critical that these organs operate normally to start with. Of course, a thyroid test should be run routinely whenever a person is suspected of having bipolar disorder, since a misbehaving thyroid gland can produce symptoms of mania or depression.
Most commonly takes a few weeks of lithium therapy to see stabilization begin. When lithium therapy is started, blood tests will be taken frequently to monitor the level in the bloodstream. The therapeutic level generally is between 0.8-1.4 milliequivalents per liter, with the higher-end levels being needed to control acute mania. Once an effective level has been found, blood tests continue but less often, because the toxic level common begins around 1.5 mEq/L or even lower - very close or even overlapping the therapeutic range.
Early signs of lithium toxicity include diarrhea, vomiting, drowsiness, muscular weakness, and lack of coordination. More severe symptoms include ataxia (failure or irregularity of muscle action), giddiness, tinnitus (ringing in the ears), blurred vision, and a large output of dilute urine.
The most common long-term effects of lithium therapy are thirst and frequent urination, tremor which may be made worse by attempting delicate hand movements, diarrhea, weight gain and edema (swelling).
Lithium can also cause a condition called nephrogenic diabetes insipidus (NDI). For more information on this condition, see the link below.
Further Reading and Resources