What is the key lab marker for monitoring the effectiveness of Lithium therapy?

The serum lithium level is the key lab marker for monitoring the effectiveness of lithium therapy. This is crucial because lithium has a narrow therapeutic window, meaning the difference between therapeutic and toxic levels is small. Regular monitoring of serum lithium concentrations helps ensure that the medication remains within this safe and effective range, allowing for adjustments in dosage as necessary.

Maintaining therapeutic levels is essential for Lithium's efficacy in managing bipolar disorder and other mood disorders, as it helps prevent both mania and depressive episodes. Additionally, monitoring serum levels aids in assessing patient adherence to the medication regimen and identifying any potential drug interactions that could affect lithium levels.

While thyroid function tests, complete blood count (CBC), and liver function tests are important for overall treatment management and monitoring potential side effects, they do not directly measure the effectiveness of lithium therapy as specifically as serum lithium levels do.