Lithium therapy involves the administration of lithium salts, primarily lithium carbonate, to manage mood disorders, particularly bipolar disorder, by stabilising mood and reducing the frequency of manic and depressive episodes. It is crucial in clinical practice due to its efficacy in preventing relapse and its unique mechanism of action on neurotransmitter systems. However, clinicians must monitor for potential complications, such as lithium toxicity, which can lead to severe neurological and renal issues.