Your insurance coverage
Given that those who have donated a kidney are healthy people and that a number of studies have shown conclusively that there is no increased risk of serious illness or kidney failure after the donation, having donated a kidney should not affect your ability to get insurance after the operation.
Note that your insurance premium is based on your overall health and not on whether or not you have donated a kidney.
However, given that every person is unique, it is important to go over the terms of your insurance coverage with your insurer.