Since Insulin is a prescription drug that is prescribed by a doctor to manage and treat diabetes then yes Medicare will cover the cost and pay for Insulin.
That's a good thing because paying out of pocket for insulin is expensive and usually not affordable for most people unless they are rich.
Medicare Part D will cover the cost of insulin and usually the supplies for insulin as well such as syringes, needles, alcohol swabs, gauze, and inhaled Insulin devices.
Medicare Part D will not cover Insulin Pumps though but they will cover the cost of Insulin.
Other health insurance might cover the cost of an Insulin pump though so check with other health insurance companies.
Some other health insurance companies may cover the cost of insulin pumps as well as Insulin and other Diabetes supplies as well.