Many types of insulin are used to treat diabetes mellitus. A few of them are listed below: 1)       Rapid-acting insulin- this insulin is taken 15min before the meals. They peak at one hour (work best to lower blood glucose) and work for another 2-4hours. Examples- are insulin lispro, insulin aspart, glulisine, etc. 2)       Short-acting insulin- they take about 30min to reach the bloodstream and reach their peak in 2-3 hours and lasts for 3-6hours. Examples- regular insulin (Humulin R) 3)       Intermediate-acting insulin: they reach the bloodstream in 2-4hours and reach a peak in 4-12 hours and work up to 18 hours.  4)       Long-acting insulin works to keep the blood sugar level stable throughout the day. Usually, they last for about 18 hours. Example- insulin glargine, insulin detemir, insulin degludec [3].