Lithium is a medicine known as mood stabiliser. It is used to treat mood disorders leading to excessive excitement, overactive & distracted mind. This drug is mainly used to control the manic phase of psychosis and in bipolar disorders. This drug can cause many side effects which may require medical attention. It is important that you take the dosage as prescribed by your doctor. Many patients stop the medicine once their condition improves while others do not take the correct dose prescribed by their doctor. This test checks whether there is compliance to the dosage prescribed for you.