Which of the following is a common sign of dehydration in a patient?

Dry mucous membranes are a common sign of dehydration because they indicate a lack of adequate fluid in the body to maintain moisture levels in the tissues. When the body is dehydrated, it loses water, leading to dryness in areas such as the mouth, lips, and other mucous membranes. This is often one of the first observable signs that healthcare providers look for when assessing a patient's hydration status.

In contrast, swelling in the extremities can be related to fluid retention rather than dehydration, and frequent urination typically suggests good hydration or conditions such as diabetes rather than dehydration. Additionally, high blood pressure is not directly indicative of dehydration; in fact, dehydration can sometimes lead to lower blood pressure due to reduced blood volume. Therefore, the presence of dry mucous membranes serves as a clear and direct sign that a patient may be experiencing dehydration.