When a patient is on lithium, what electrolyte level should be closely monitored?

When a patient is on lithium, it is essential to closely monitor sodium levels because lithium competes with sodium in the body and can lead to alterations in sodium balance. Lithium is primarily used as a mood stabilizer in the treatment of bipolar disorder, and its effectiveness and safety can be significantly impacted by sodium levels.

If sodium levels drop, such as during dehydration or the use of diuretics, there is a risk of lithium toxicity. This is because the body can increase lithium reabsorption in the kidneys when sodium is low, potentially leading to elevated lithium levels which can have serious side effects, including neurological complications. Therefore, maintaining stable sodium levels is crucial for preventing toxicity and ensuring effective treatment with lithium. Regular monitoring of sodium, therefore, helps in managing the risks associated with lithium therapy effectively.