Insulin glargine is a long-acting type of insulin that works slowly, over about 24 hours. Insulin is one of many hormones that help the body turn the food we eat into energy. This is done by using the glucose (sugar) in the blood as quick energy. Also, insulin helps us store energy that we can use later. When you have diabetes mellitus, your body cannot make enough insulin or does not use insulin properly. This causes you to have too much sugar in your blood. Like other types of insulin, insulin glargine is used to keep your blood sugar level close to normal. You may have to use insulin glargine in combination with another type of insulin or with a type of oral diabetes medicine to keep your blood sugar under control.