A 34-year-old client with diagnosed celiac disease presents with a new onset of diarrhea and fatigue despite adhering to a gluten-free diet. What action should the nurse take to address these symptoms?

When a client with celiac disease on a gluten-free diet develops new or recurring symptoms such as diarrhea and fatigue, the first and most appropriate nursing action is to encourage a thorough dietary review for potential hidden gluten exposure. Many processed foods, medications, condiments, and even cross-contaminated products can contain trace amounts of gluten that trigger symptoms without the patient's awareness. This is the most common reason for symptom recurrence in adherent patients, and identifying dietary sources of inadvertent gluten exposure is both cost-effective and clinically sound as an initial step. Suggesting over-the-counter probiotics may have some general gut health benefits but does not address the likely cause of symptom recurrence and should not be the first recommendation. Increasing fiber intake could worsen diarrhea in someone with active intestinal inflammation and is not an evidence-based first response to celiac symptom recurrence. Referring for endoscopy is a valid step if dietary review reveals strict compliance and symptoms persist, but it is invasive and premature as an initial intervention before evaluating for simpler explanations such as inadvertent gluten ingestion. The dietary review logically precedes further diagnostic workup.