Final answer:
A nurse should monitor a client prescribed phenytoin for Vitamin B deficiency, as it is a known side effect of the medication.
Step-by-step explanation:
For which adverse effect should the nurse monitor a client prescribed phenytoin (Dilantin)? The correct answer is Vitamin B deficiency. Phenytoin is an anticonvulsant medication used to manage seizures, but it has several potential side effects, including the decreased absorption of vitamins, especially Vitamin B, leading to deficiency. Monitoring for signs of Vitamin B deficiency is important as it may manifest through symptoms such as loss of appetite, edema, nervous system defects, and cardiovascular changes. While phenytoin does not directly lead to hypoglycemia, leg edema, or bleeding, these are not typically associated side effects of the medication when taken at therapeutic levels.