For a client taking phenytoin with a blood level of 35 mcg/mL, which symptom would be anticipated?

A blood level of phenytoin at 35 mcg/mL is considered above the therapeutic range, as the typical therapeutic range for phenytoin is generally between 10 to 20 mcg/mL. When levels exceed this range, it can result in several neurological side effects due to toxicity.

Slurred speech is a common symptom that may be observed in clients experiencing phenytoin toxicity. This occurs because phenytoin can depress the central nervous system when present in higher concentrations, affecting motor function and coordination, leading to difficulties with speech articulation.

The other options—namely increased energy levels, improved coordination, and headache relief—are unlikely to be observed in a client with elevated phenytoin levels. Increased energy levels and improved coordination would typically be associated with optimal or low levels of the medication, not toxicity. Similarly, headache relief is not a direct effect of elevated phenytoin levels; instead, it can lead to more adverse effects, including headaches due to possible CNS irritation. Thus, slurred speech stands out as the expected symptom in this scenario.