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PR-66 Denial Code: Blood Deductible

CARC 66 is the blood deductible. Some plans, most notably Medicare, don't pay for the first few units of whole blood or packed red cells a patient receives each year unless the blood is replaced. The group code shows who is responsible; it's usually the patient (PR).

Quick facts

Code
PR-66 (CARC 66)
Status
Active In use since January 1, 1995.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • PR (Patient Responsibility): The typical group. The patient owes the blood deductible unless the blood is replaced by a donation on their behalf or other coverage pays it.
  • CO (Contractual Obligation): Used when the provider absorbs the deductible, for example because the provider doesn't charge for blood it obtained at no cost, or a contract term applies. The patient isn't billed.
Official description
Blood Deductible.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CARC 66 means

CARC 66 is the blood deductible. Some health plans treat whole blood and packed red cells differently from other services: the patient is responsible for the first few units they receive in a year unless the blood is replaced. The payer reports the portion subject to that rule with CARC 66.

Medicare is the best-known example. It generally doesn’t pay for the first 3 units of blood a beneficiary receives in a calendar year. That deductible applies once a year across Part A and Part B, and it’s satisfied when the blood is replaced through donation. The deductible covers the blood itself, not the transfusion services or blood processing, which are billed and paid separately under normal rules.

The group code tells you who carries the amount. With PR-66, the patient (or their supplemental coverage) owes it. With CO-66, the provider absorbs it.

Common causes

  • Patient’s first units of blood in the year, under a plan with a blood deductible.
  • Blood not replaced by donation.
  • Blood deductible already met at another facility earlier in the year, but not yet reflected in the payer’s records.
  • Claim reporting errors, such as incorrect value codes for blood units furnished or replaced on institutional claims.

How to handle it

  1. Confirm the number of units furnished and replaced on the claim.
  2. Check the patient’s year-to-date blood deductible status with the payer.
  3. Bill the supplemental payer if the patient has Medigap or other secondary coverage.
  4. Bill the patient for any remaining PR-66 amount, or write off a CO-66 amount.
  5. Correct and resubmit if units furnished or replaced were reported wrong, using the payer’s adjustment process for institutional claims.

How to prevent problems

  • Record blood replacement when donations are made on the patient’s behalf.
  • Report blood value codes accurately on institutional claims.
  • Tell patients about the blood deductible before elective procedures that may need transfusion.

Specialty notes

Hospitals, blood banks, and outpatient infusion or dialysis facilities encounter the blood deductible most often. It mainly appears on institutional claims, though professional claims for blood products can also be affected.

Remark codes that may appear with PR-66

  • N130 (Consult plan benefit documents/guidelines for information about restrictions for this service.): Points to plan documents describing the blood deductible.
  • PR-1 (Deductible Amount): The standard deductible, separate from the blood deductible.
  • PR-2 (Coinsurance Amount): Coinsurance, which may also apply to blood-related services.
  • PR-247 (Deductible for Professional service rendered in an Institutional setting and billed on an Institutional claim.): A deductible for a professional service billed on an institutional claim.
  • OA-23 (The impact of prior payer(s) adjudication including payments and/or adjustments. (Use only with Group Code OA)): The prior payer's adjudication, relevant when a secondary payer picks up the blood deductible.

PR-66 FAQ

How does Medicare's blood deductible work?

Medicare generally doesn't pay for the first 3 units of blood a beneficiary receives in a calendar year. The deductible applies once per year across Part A and Part B combined, and it's met if the blood is replaced by donation.

Can a supplemental plan pay the blood deductible?

Many Medigap plans cover the Medicare blood deductible. Send the claim to the supplemental payer with the Medicare remittance.

What does blood replacement mean?

The patient or someone on their behalf donates blood to replace what was used. When blood is replaced, the provider shouldn't charge the deductible for those units.

Does the blood deductible apply to plasma or platelets?

Medicare's blood deductible applies to whole blood and packed red cells. Other blood components are generally handled under standard coverage rules. Check the payer's policy for other plans.