A nurse is reviewing abnormal laboratory values for four clients who have schizophrenia and take clozapine. For which of the following clients should the nurse withhold the medication and notify the provider immediately to have clozapine therapy discontinued?

Choice A reason: A serum potassium of 3.3 mEq/L is slightly low but does not require stopping clozapine therapy. Choice B reason: A hematocrit of 55% is elevated but not a contraindication for clozapine use. Choice C reason: A WBC of 2,900 cells/mm³ indicates severe leukopenia/agranulocytosis, a life-threatening adverse effect of clozapine, requiring immediate discontinuation. Choice D reason: A BUN of 22 mg/dL is only mildly elevated and not directly related to clozapine risks.