A nurse is making a home visit to an older adult woman who was recently discharged home from the hospital with a new prescription. The nurse notes that a serum drug level drawn the day before was subtherapeutic. What will the nurse do next?

A. Request an order for renal function tests: Renal function tests are important when monitoring for drug toxicity or impaired clearance, especially in older adults. However, a subtherapeutic level suggests underdosing or nonadherence rather than impaired elimination. B. Notify the provider to request more frequent dosing: Changing the dosing regimen without first confirming whether the patient is taking the medication correctly could lead to inappropriate adjustments and potential harm. The nurse must first investigate possible causes of the low drug level. C. Count the pills in the prescription bottle: Checking the number of pills helps determine whether the patient has been taking the medication as prescribed. Nonadherence is a common cause of subtherapeutic drug levels in older adults and should be assessed before considering other actions. D. Ask the patient if she has difficulty swallowing pills: Difficulty swallowing could affect adherence, but directly counting the pills provides a more objective measure of whether the medication is being taken consistently.