To appeal an Original Medicare denial, start with the Medicare Summary Notice (MSN) that shows the denied service, and file a written "redetermination" request by the date printed on it. You can use Medicare's Redetermination Request Form or follow the instructions on the MSN's last page, and you'll generally get a decision within 60 days. If you still disagree, there are four more levels of appeal, each with its own deadline.
How do I know Medicare denied something?
Look at your MSN. Page 1 asks "Did Medicare approve all services?" and lists the number of services Medicare denied. On the claims pages, a denied service shows "NO" in the "Service approved?" column, and the "Maximum You May Be Billed" usually equals the full charge. A note letter next to the line explains the reason.
If you're in a Medicare Advantage plan, the process is different. Your plan sends a denial notice, and you appeal to the plan first. See our separate guide on Medicare Advantage appeals.
Step 1: Should I call the provider before I appeal?
Yes, in most cases. Medicare.gov suggests asking your provider for any information that would make your appeal stronger. A phone call can also uncover a simple fix. Some denials come from a missing diagnosis code or a coding error, and the office can correct and resubmit the claim.
You might say: "Medicare denied the [service] from [date]. The note says [reason]. Can you check whether the claim had the right codes and diagnosis? If it did, can you send me a letter or records explaining why I needed this service?"
Step 2: Did I sign an Advance Beneficiary Notice?
Check your papers for an Advance Beneficiary Notice of Noncoverage (ABN), Form CMS-R-131. The Centers for Medicare & Medicaid Services (CMS) says providers and suppliers give this form to people with Original Medicare when they expect Medicare to deny payment, and it shifts potential financial responsibility to you.
Medicare's "Medicare Appeals" booklet explains the three ABN options. If you chose Option 1, you asked the provider to bill Medicare. If Medicare denies the claim, you're responsible for paying, but you can still appeal, and if Medicare does pay, the provider refunds what you paid minus your copayments and deductibles. If you chose Option 2 (don't bill Medicare), no claim is filed and you can't appeal.
Step 3: Find your deadline
The deadline is printed on the last page of your MSN, under "We must receive your appeal by." Medicare's sample MSN says the claims office must get your appeal within 120 days from the date you get the notice.
If you miss it, Medicare.gov says you may still be able to appeal if you can show good cause, like an illness, disability, or accident that kept you from filing on time.
Step 4: File a Level 1 appeal (redetermination)
You have two ways to file.
Option A: Use the Redetermination Request Form (CMS-20027). Fill it out and mail it to the Medicare Administrative Contractor (MAC). The address is on the last page of your MSN.
Option B: Use your MSN.
- Circle the item you're appealing on a copy of the MSN.
- Explain in writing why you disagree, on the MSN or a separate sheet.
- Write your name, phone number, and Medicare Number.
- Add anything that helps, like a letter from your doctor or medical records.
- Mail it to the address on the last page of the MSN.
Either way, keep copies of everything you send. Write your Medicare Number on every page. Sending it by a trackable mail method gives you proof of the date it arrived.
Step 5: What should I write in the appeal?
Keep it short and specific. A few sentences often work:
"I am appealing the denial of [service] on [date of service], claim number [number from MSN]. My doctor ordered this service because [reason, e.g., my symptoms or diagnosis]. I have enclosed a letter from Dr. [name] explaining why it was medically necessary. Please reconsider and approve this claim."
A letter from your doctor that explains why you needed the service is usually the most useful thing you can include.