Answer
The short answer
More than most letters say. Federal rules require the specific reason, the plan provision, what else you would need to send, the denial code, and the internal criterion, free on request. Ask for whatever is missing.
A denial is not a decision the plan gets to announce however it likes. The claims-procedure regulation requires the notice to be written or electronic and set out in a manner calculated to be understood by the claimant, and then lists what it has to say.
Read your letter against this list. Most letters that feel unanswerable are unanswerable because an item is missing, not because the decision is airtight.
The list above comes from the general claims-procedure rule. Group and individual health coverage carries a second layer on top of it, and this is the layer most people have never been told about.
Your notice has to identify the claim — the date of service, the provider, the amount where it applies — and tell you that the diagnosis code and the treatment code, with what each one means, are available if you ask. It has to give the denial code and its meaning, plus the plan's standard, if any, that was used in denying the claim. A final internal denial has to go further and include a discussion of the decision.
It also has to describe the internal appeal and external review routes and how to start one, and to give you the contact details for any consumer assistance office or ombudsman in your state that helps with exactly this.
Yes, and the regulation says so specifically, because otherwise asking a question would cost you a route. The plan must not treat a request for the diagnosis and treatment information as, by itself, a request for an internal appeal or an external review.
That is worth knowing before you telephone. You can ask what the codes were, what standard they applied and what criterion you failed, and still have your appeal in front of you.
On appeal, yes, and at no cost. The plan has to provide, on request and free of charge, reasonable access to and copies of all documents, records and other information relevant to your claim. Relevant is defined broadly on purpose: it covers what was relied on, what was generated or considered along the way whether or not it was relied on, and the plan's own statements of policy about the treatment for your diagnosis.
The health-plan layer adds a second right that changes how an appeal feels: you may review the claim file and present evidence and testimony. And if the plan generates new evidence while your appeal is running, it has to send it to you far enough ahead of the final decision for you to answer it. They cannot spring it on you in the denial.
Eventually, and quickly. For an urgent-care claim the plan may give you the information orally within the urgent timeframe, but a written or electronic notice carrying everything in the list above has to follow within three days.
If you got a phone call refusing something urgent and nothing arrived afterwards, that is not how the rule reads.
A similar one, on its own rules, and it is shorter. A Part D plan that denies a drug benefit must give you written notice; it may tell you orally first, but the written follow-up has to be mailed within three calendar days.
What that notice has to do is use approved language in a readable and understandable form, state the specific reasons for the denial, describe both the standard and expedited redetermination processes and the rest of the appeals process, and tell you about your right to a redetermination.
The practical difference from a commercial denial is that the Part D list does not carry the free-of-charge internal-criterion sentence. Ask for the criteria anyway — but do not go in citing a rule that does not govern your plan.
There is a consequence, and it is bigger than a correction. If a plan fails to establish or follow claims procedures consistent with the regulation, you are deemed to have exhausted the plan's internal remedies and may go straight to the courts.
For health coverage the standard is tighter still: a plan that fails to adhere strictly to the internal appeals requirements is deemed to have had its process exhausted, and you may initiate an external review. There is a limit — a violation that is minor, harmless, in good faith and not part of a pattern does not trigger this, and you can demand a written explanation of it, which the plan has ten days to give you.
None of that is a reason to skip your appeal. It is a reason to keep the letter, note what is not in it, and ask in writing for the rest.
What to say on the phone
I received a denial dated [date] for [drug name]. Please send me the internal rule or clinical criterion this decision was made against, and the explanation of the clinical judgment applied to my circumstances. The notice says these are available free of charge on request, and I am requesting them. Please also confirm the denial code and its meaning, and the diagnosis and treatment codes on the claim. I understand this request is not itself an appeal.
Ask for it in writing and note the date you asked. If they tell you a document does not exist, ask them to put that in writing too.
If something here decides anything for you, read the source rather than our summary of it. These are the documents we opened, and the month we opened them.
A denial notice must be understandable and must contain a defined list. The regulation requires that "The notification shall set forth, in a manner calculated to be understood by the claimant—" and then lists "The specific reason or reasons for the adverse determination;" and "Reference to the specific plan provisions on which the determination is based;" along with "A description of any additional material or information necessary for the claimant to perfect the claim and an explanation of why such material or information is necessary;" and "A description of the plan's review procedures and the time limits applicable to such procedures, including a statement of the claimant's right to bring a civil action under section 502(a) of the Act following an adverse benefit determination on review;".
29 CFR §2560.503-1(g)(1), Electronic Code of Federal Regulations, effective August 2026 · source · read August 2026
Where the plan used an internal criterion, you can have it for nothing. The notice must give either the rule itself or "a statement that such a rule, guideline, protocol, or other similar criterion was relied upon in making the adverse determination and that a copy of such rule, guideline, protocol, or other criterion will be provided free of charge to the claimant upon request." Where the denial rests on medical necessity or an experimental exclusion, the notice must give "an explanation of the scientific or clinical judgment for the determination, applying the terms of the plan to the claimant's medical circumstances," or a statement that it will be provided free of charge on request.
29 CFR §2560.503-1(g)(1)(v), Electronic Code of Federal Regulations, effective August 2026 · source · read August 2026
An urgent denial can be delivered by telephone, but writing has to follow fast. For a group health plan claim involving urgent care the information "may be provided to the claimant orally within the time frame prescribed in paragraph (f)(2)(i) of this section, provided that a written or electronic notification in accordance with paragraph (g)(1) of this section is furnished to the claimant not later than 3 days after the oral notification."
29 CFR §2560.503-1(g)(2), Electronic Code of Federal Regulations, effective August 2026 · source · read August 2026
Health coverage carries extra notice requirements the general rule does not. The plan must ensure the notice includes "information sufficient to identify the claim involved (including the date of service, the health care provider, the claim amount (if applicable), and a statement describing the availability, upon request, of the diagnosis code and its corresponding meaning, and the treatment code and its corresponding meaning)." It must also ensure the stated reason "includes the denial code and its corresponding meaning, as well as a description of the plan's or issuer's standard, if any, that was used in denying the claim," and for a final internal denial "this description must include a discussion of the decision." It must "provide a description of available internal appeals and external review processes, including information regarding how to initiate an appeal," and "disclose the availability of, and contact information for, any applicable office of health insurance consumer assistance or ombudsman."
45 CFR §147.136(b)(2)(ii)(E), Electronic Code of Federal Regulations, effective August 2026 · source · read August 2026
Asking for the codes does not use up your appeal. The regulation states that the plan "must not consider a request for such diagnosis and treatment information, in itself, to be a request for an internal appeal under this paragraph (b) or an external review under paragraphs (c) and (d) of this section."
45 CFR §147.136(b)(2)(ii)(E)(2), Electronic Code of Federal Regulations, effective August 2026 · source · read August 2026
On appeal your file is yours, free. The plan must "Provide that a claimant shall be provided, upon request and free of charge, reasonable access to, and copies of, all documents, records, and other information relevant to the claimant's claim for benefits." Relevant is defined widely: it includes anything that "Was submitted, considered, or generated in the course of making the benefit determination, without regard to whether such document, record, or other information was relied upon," and any plan "statement of policy or guidance with respect to the plan concerning the denied treatment option or benefit for the claimant's diagnosis."
29 CFR §2560.503-1(h)(2)(iii) and (m)(8), Electronic Code of Federal Regulations, effective August 2026 · source · read August 2026
Health coverage adds the right to see the file and answer new evidence. The rule says a plan "must allow a claimant to review the claim file and to present evidence and testimony as part of the internal claims and appeals process," and that any new or additional evidence the plan generates or relies on "must be provided as soon as possible and sufficiently in advance of the date on which the notice of final internal adverse benefit determination is required to be provided... to give the claimant a reasonable opportunity to respond prior to that date."
45 CFR §147.136(b)(2)(ii)(C), Electronic Code of Federal Regulations, effective August 2026 · source · read August 2026
A Medicare Part D denial runs on its own notice rule. "If a Part D plan sponsor decides to deny a drug benefit, in whole or in part, it must give the enrollee written notice of the determination. The initial notice may be provided orally, so long as a written follow-up notice is mailed to the enrollee within 3 calendar days of the oral notification." That notice must "Use approved notice language in a readable and understandable form," "State the specific reasons for the denial," describe "both the standard and expedited redetermination processes... and the rest of the appeals process," and "Inform the enrollee of his or her right to a redetermination."
42 CFR §423.568(f) and (g), Electronic Code of Federal Regulations, effective August 2026 · source · read August 2026
A plan that does not follow the rules loses the right to make you keep using them. Where a plan fails "to establish or follow claims procedures consistent with the requirements of this section, a claimant shall be deemed to have exhausted the administrative remedies available under the plan." The health-coverage version is stricter and points somewhere more useful: a plan that "fails to strictly adhere to all the requirements" is deemed exhausted, so "the claimant may initiate an external review." That does not apply to "de minimis violations that do not cause, and are not likely to cause, prejudice or harm to the claimant" where the plan shows good cause and the lapse was not part of a pattern.
29 CFR §2560.503-1(l)(1) and 45 CFR §147.136(b)(2)(ii)(F), Electronic Code of Federal Regulations, effective August 2026 · source · read August 2026
American GLP is not a law firm, an insurer, a government office or a clinician, and nothing here is legal or medical advice. This page describes what published rules say. Your own plan documents and your own notice govern your case, and rules change — check the sources before you act.