This test is for those taking prescription lithium. The test does NOT provide a normal reference range for lithium, it only provides a therapeutic reference range to ensure adequate dosing of prescription lithium. It may be used to measure blood levels every few days when a person first begins taking lithium to help adjust the dose and reach the desired blood level. The test may also be used at regular intervals to monitor blood concentrations. Lithium is used to treat mood disorders. Lithium blood tests need to be taken at least 12 hours after the last dose of lithium to make sure the test is reliable. Fasting is not required for this test. Take all medications as prescribed.