Which of the following symptoms might indicate excessive bleeding due to heparin use?

The presence of blood in stool is a significant indicator of excessive bleeding when someone is using heparin, an anticoagulant. Heparin works by inhibiting the clotting factors in the blood, thus preventing blood clots. However, this anticoagulation effect can lead to an increased risk of bleeding complications, including gastrointestinal bleeding. When blood is present in the stool, it may indicate that the gastrointestinal tract has been compromised due to bleeding, which is a serious concern in patients receiving heparin therapy.

Recognizing such symptoms is critical as they require immediate evaluation and intervention to prevent severe complications that can arise from excessive bleeding, such as hypovolemic shock or the need for blood transfusions. Other options like increased thirst, renal failure, and fatigue may suggest other conditions or complications but are not directly indicative of excessive bleeding due to heparin use. Thus, identifying blood in the stool is a key symptom that warrants immediate clinical attention in the context of heparin administration.