Final answer:
The nurse should suggest taking lithium with meals to help minimize gastrointestinal discomfort by reducing the direct contact of the medication with the stomach lining.
Step-by-step explanation:
When a patient reports that lithium causes an upset stomach, it is often suggested to take the medication with meals. Therefore, the correct advice for a patient experiencing this side effect would be to take lithium with meals. This helps to minimize gastrointestinal discomfort by mixing the medication with food, thereby reducing the direct contact of the medication with the stomach lining.
While taking lithium with an antacid might also be considered if the problem persists, the initial recommendation is to take it with meals to ease the discomfort. Taking lithium 30 minutes before meals or 2 hours after meals could actually worsen the upset stomach, as the medication would come into direct contact with an empty stomach, potentially irritating it further.