Which statement indicates the need for further instruction for a client on lithium carbonate?

The statement indicating the need for further instruction is related to the use of over-the-counter medications with lithium carbonate. Lithium is a mood stabilizer used primarily for the treatment of bipolar disorder, and it has a narrow therapeutic index, meaning the difference between an effective dose and a toxic dose is small. Therefore, taking any over-the-counter medications can potentially interfere with lithium metabolism or increase the risk of side effects.

Certain medications, such as NSAIDs (non-steroidal anti-inflammatory drugs), can elevate lithium levels and lead to toxicity, while others might affect kidney function or fluid balance, which are crucial for lithium's efficacy and safety. It is important for clients on lithium carbonate to consult with their healthcare provider before starting any new medications, including over-the-counter options.

The other statements reflect appropriate knowledge regarding lithium therapy. Avoiding excessive sodium intake is important as fluctuations in sodium levels can affect lithium levels. Additionally, staying well-hydrated is critical because dehydration can also influence lithium levels. Finally, diarrhea and muscle weakness should not be regarded as expected symptoms without further evaluation, but they can indicate potential side effects or toxicity if they occur.