Final answer:
Isotretinoin can cause hyperglycemia, which is a condition characterized by high blood sugar levels.
Step-by-step explanation:
The side effects of isotretinoin (Accutane) can include a range of symptoms and abnormalities. In the case of a client with a history of diabetes mellitus, a high blood glucose level like 268 mg/dL (option b) might indicate a side effect of the drug. Isotretinoin can cause hyperglycemia, which is a condition characterized by high blood sugar levels.