Treating diabetes with an insulin pump is one of the bests ways to get good control of blood sugar levels.
When a diabetic is on mdi's, they need to eat a certain amount of carbs for each meal and at the same time. With a pump, if the person isn't hungry, they don't need to eat. Also a pump works in a similar way to a pancreas in a non diabetic person.
For a person to be on an insulin pump, a basal rate is worked out for the diabetic to get over 24 hours. This is in place of the background insulin a person on mdi's has.
Then a bolus rate is worked out for each time the person eats. The pump will have a ratio of how much insulin is needed for each gram of carb. When the diabetic person eats they will enter into the pump, how many carbs they are eating and the pump will deliver a bolus of insulin.
As well as working out the carb ratio, the pump will have a correction rate for high blood sugars so when the diabetic has a high sugar, they can enter into the pump their reading and the pump will deliver a bolus to bring the sugar level back to it's target.
A pump site needs to be changed every 3 to 4 days. Here is a video of someone changing a mini med pump. Tom uses the mini med 520.