Which of the following is a common symptom of diabetes?

Excessive thirst, or polydipsia, is a common symptom of diabetes and is primarily related to the body's response to high blood glucose levels. When blood sugar rises, the kidneys must work harder to filter and absorb the excess glucose. This process leads to increased urination, which in turn causes the body to lose more fluids, resulting in dehydration. The body's natural response to dehydration is to trigger feelings of thirst to encourage fluid intake. Therefore, individuals with diabetes often experience a persistent need to drink water and can feel excessively thirsty as a result of their condition.

In contrast, increased energy levels would not typically be associated with diabetes; rather, many individuals may experience fatigue due to insulin resistance or insufficient insulin production. Improved vision is not a common symptom of diabetes; in fact, diabetes can lead to vision issues over time, such as blurred vision or more serious conditions like diabetic retinopathy. Weight gain is also not considered a classic symptom of diabetes; it can occur with type 2 diabetes, but it is often more associated with factors like lifestyle and diet rather than being a direct symptom.