Which diabetic medication is contraindicated for exercise?

The correct option identifies insulin as a medication that may pose risks when engaging in exercise. Insulin therapy is essential for many individuals with diabetes as it helps regulate blood glucose levels. However, its management during physical activity requires careful consideration due to the potential for hypoglycemia—a condition where blood sugar levels fall dangerously low.

When someone takes insulin, especially before exercise, there's a risk that their blood sugar can drop significantly during physical activity. This is particularly true if the individual hasn't properly adjusted their carbohydrate intake or insulin dosage prior to working out. Because exercise increases insulin sensitivity and glucose uptake by muscles, athletes or active individuals may need to monitor their blood sugar levels more closely and make necessary adjustments to their insulin regimen around their exercise schedule.

In contrast, medications like metformin, glipizide, and acarbose do not carry the same immediate risk of hypoglycemia when compared to insulin during exercise. While they can also affect blood sugar levels, they do not result in acute changes that would contraindicate physical activity. Thus, while individuals on any diabetic medication should be attentive to their blood sugar management during exercise, insulin requires the most caution due to its strong and immediate effects on glucose regulation.