How to decode an insurance denial letter in 2 minutes

Insurance denial letters are written by lawyers, reviewed by lawyers, and apparently tested on no actual humans. You get a page of codes, a sentence like "this service is not medically necessary per plan guidelines," and a vague invitation to appeal within some number of days. Somewhere in there is the actual reason they didn't pay. Good luck finding it on your own at 9pm.

Here's the faster way.

What to send

Forward the denial letter or EOB (the PDF from your insurer's portal, or even a photo of the paper copy) to [email protected] with a line like:

"Got this denial for my daughter's MRI. Can you tell me what reason code CO-50 actually means, whether this looks appealable, and what I should say when I call?"

That's it. Mabel reads the PDF directly, so you don't need to retype anything.

What comes back

A plain-English breakdown, usually within a few minutes:

What happened: The claim was denied under code CO-50, which means the insurer decided the service wasn't medically necessary under your plan's rules. This is one of the most commonly overturned denial types.

What it's not: This is not a coverage exclusion. The MRI is a covered service; they're disputing whether it was needed.

What to do next: Call the member services number on the letter and ask three things: which specific guideline the reviewer used, whether your doctor can request a peer-to-peer review, and the deadline for a written appeal.

She'll also flag the appeal deadline if it's buried in the letter, because it usually is, and it's usually shorter than you'd guess.

One thing worth saying plainly: Mabel isn't a doctor or a lawyer. She decodes the letter, explains the codes, and arms you with sharper questions. The medical judgment stays between you and your doctor; the appeal decision stays with you.

And since denial letters tend to contain things like diagnosis codes and member IDs: Mabel never has access to your inbox or your insurer's portal. She only sees the one document you choose to forward, and the conversation is kept only while it's active — up to 24 hours after your last message — then deleted automatically. Forwarded files themselves are gone as soon as she's replied.

Pro tip

Include one sentence of context about why the service was ordered. "My doctor ordered this after two months of physical therapy didn't help" changes the answer, because failed conservative treatment is exactly the kind of detail that makes a medical-necessity appeal stick. The more Mabel knows about the situation, the more specific her suggested questions get, and specific questions are what get claims overturned.

A denial letter is the start of a negotiation, not the end of one. Most people never appeal; insurers know this. Two minutes of decoding puts you in the small group that does.