Which of the following symptoms may present in lithium toxicity?

Lithium toxicity is characterized by several symptoms that reflect the effects of elevated lithium levels in the body. Nausea and diarrhea are commonly reported side effects and symptoms of lithium toxicity. When lithium levels rise to toxic levels, they can irritate the gastrointestinal tract, leading to nausea and gastrointestinal disturbances, including diarrhea.

These symptoms occur due to lithium's impact on cellular processes and its concentration in the gastrointestinal system, which can lead to significant fluid loss and contribute to dehydration. Nausea in particular is often one of the first symptoms noticed when toxicity begins to develop.

In contrast, other symptoms mentioned in the remaining options may occur due to a variety of factors but are not typically associated with lithium toxicity specifically. For instance, headaches and dizziness often stem from other conditions or medication side effects, while skin rashes and pallor may indicate different dermatological or systemic issues rather than lithium-related toxicity. Increased appetite and dehydration are also not characteristic of lithium toxicity, as elevated lithium levels more commonly lead to decreased appetite and potential fluid imbalance due to excessive loss through vomiting or diarrhea.