What complication arises when lithium levels exceed 1.5 mEq/L?

When lithium levels exceed 1.5 mEq/L, the most significant and acute complications include ataxia and vomiting. Elevated lithium levels can lead to toxicity, which manifests through a range of neurologic and gastrointestinal symptoms. Ataxia refers to a lack of muscle coordination, which can severely impact a person's ability to walk or perform fine movements. Vomiting is a common gastrointestinal symptom associated with lithium toxicity, reflecting the body's rapid response to high serum levels of the medication.

Managing lithium levels is crucial because toxicity can escalate quickly and lead to more severe complications, including seizures and potential renal impairment. Therefore, monitoring serum lithium levels is essential in patients undergoing treatment with lithium for mood disorders to prevent complications associated with excessive levels.