What serum lithium level might raise concern for a physician monitoring a patient on lithium carbonate?

A serum lithium level of 1.8 mEq/L is significant because it falls into the range that indicates a risk of lithium toxicity. Lithium has a narrow therapeutic window, typically ranging from 0.6 to 1.2 mEq/L for optimal efficacy in treating conditions like bipolar disorder. When levels exceed this range, particularly above 1.5 mEq/L, the chances of experiencing adverse effects increase markedly.

At 1.8 mEq/L, patients may begin to exhibit symptoms of toxicity, which can include gastrointestinal distress, tremors, confusion, agitation, muscle weakness, and in more severe cases, seizures and coma. Continuous monitoring is essential for patients on lithium, and levels approaching or above 1.5 mEq/L would warrant immediate evaluation and potential intervention.

In contrast, levels lower than this, such as 0.8 or 1.2 mEq/L, are generally within the therapeutic range and do not usually raise immediate concern for toxicity. Thus, the level of 1.8 is critical for physicians to be aware of during the management of patients receiving lithium therapy.