Final answer:
Medicare is the primary source of payment for most patients who have been on dialysis for over 30 months, as it covers the costs after a patient's private insurance coordination period ends.
Step-by-step explanation:
The source of payment for most patients who have been on dialysis for over 30 months typically transitions to Medicare coverage. Medicare is a federal health insurance program in the United States that starts covering the costs of dialysis after a 30-month coordination period if the patient had been utilizing private insurance. For those who do not have private insurance, Medicare may become the primary payer even sooner. Dialysis is critical for patients with kidney failure, as it artificially removes waste products and excess fluid from the blood, a function normally performed by functioning kidneys.