What symptom indicates possible lithium toxicity that requires further assessment?

Nausea and vomiting are significant symptoms that can indicate lithium toxicity and require immediate further assessment. Lithium has a narrow therapeutic window, and its toxicity can manifest with gastrointestinal symptoms, including nausea and vomiting. When a patient on lithium develops these signs, it suggests that the serum lithium levels may be approaching toxic levels, which can lead to serious complications and affect the kidneys and neurological function.

In the context of lithium therapy, monitoring for these signs is crucial as they may precede more severe symptoms of toxicity such as tremors, confusion, or seizures. Prompt assessment and intervention are necessary to ensure the patient remains within the therapeutic range and to prevent any potential acute harm.

While increased thirst, fatigue, and decreased appetite may also occur in patients taking lithium, they are more commonly associated with its therapeutic effects or mild side effects rather than direct indicators of toxicity. Hence, they do not require the same immediate level of concern as nausea and vomiting would.