Medigap Plan D is a private insurance plan that supplements Original Medicare (Parts A and B) by covering out-of-pocket costs like deductibles and coinsurance—except the Part B deductible. It pays for the Part A deductible, hospice care coinsurance, Part B coinsurance or copay, the first three pints of blood, and skilled nursing facility coinsurance. It does not cover the Part B deductible, excess charges, or prescription drugs, which require a separate Part D plan.