Final answer:
Long-acting insulins like insulin glargine or detemir have the longest action, while rapid-acting insulins such as lispro, aspart, or glulisine act the fastest.
Step-by-step explanation:
The insulin with the longest action is typically a long-acting insulin such as insulin glargine or insulin detemir. These insulins start working several hours after injection and keep working evenly for 24 hours or more, making them suitable for maintaining baseline insulin levels. On the other hand, the insulin with the fastest action is rapid-acting insulin, such as insulin lispro, insulin aspart, or insulin glulisine. Rapid-acting insulins work within 15 minutes of injection, peak at around 1 hour, and continue to work for 2 to 4 hours. These insulins are used to manage blood sugar levels during meals or when a fast response is required.