Denied as “Experimental or Investigational”? How to Appeal

Written by Aptiva Health Editorial Team · Medically reviewed by Thomas Huhn, MD · Reviewed by Taylor Sorrels, Esq. and Crystal Brake, RCM Director · Editorial & review standards · How we research

Sometimes a health plan says no because it thinks a treatment, test or device is experimental or investigational. That means the plan does not believe there is enough proof that the care works, or that it is the accepted way to treat your condition.

This denial can feel like a dead end. It is not. Because it is a decision about medicine, it is the kind of denial that independent outside review was built for. Federal rules and both Kentucky and Indiana law let you ask for an outside review of experimental or investigational denials after your internal appeal.

This guide explains what the denial means, what evidence can help, and how to appeal. It is part of the Coverage & Appeals Center.

What the codes and words mean

Your Explanation of Benefits (EOB) or your provider’s payment notice may show a reason code. Two codes often go with this kind of denial. Here is the official wording (X12: Claim Adjustment Reason Codes):

Letters may use other words too, such as “unproven,” “not medically proven,” or “not the standard of care.” Each plan writes its own policies, so the same care may be covered by one plan and denied by another.

You can use the denial decoder to look up other codes on your EOB.

Why this denial is different

Many denials are about paperwork. This one is about medical judgment. That matters, because outside review is open to denials that involve medical judgment.

• Federal rules. External review covers denials based on medical judgment, including a decision that care is experimental or investigational (45 CFR 147.136(d)). The outside reviewer’s decision is binding on the plan. If it reverses the denial, the plan must “immediately” provide coverage or payment.
• Kentucky. External review covers denials that say care is “experimental or investigational” (KRS 304.17A-600). The independent reviewer’s decision is binding on the insurer (KRS 304.17A-625).
• Indiana. External review covers a “determination that a proposed service is experimental or investigational” (IC 27-8-29-12). The decision is binding on the insurer (IC 27-8-29-16).

In Indiana, the internal appeal of an experimental denial is decided by a panel that includes a reviewer in the same profession and a similar specialty. You may also appear in person (IC 27-8-28-17).

Evidence that can help

You win this kind of appeal by showing that the care is accepted and right for you. What counts as strong evidence is a medical question, so work with your clinician.

• The plan’s own policy. Ask for a free copy of the policy or guideline the plan used (29 CFR 2560.503-1(g)(1)(v)). Check its date. A policy written years ago may not reflect newer research.
• A letter from your clinician. It should explain your diagnosis, what was already tried, why standard options did not work or are not safe for you, and why this care is the right next step.
• Published research. Your clinician may cite studies in medical journals that show the care works for people like you.
• Professional guidelines. Guidance from a national medical society that supports the care can carry weight.
• FDA status, if it applies. For a drug or device, your clinician can explain whether it is approved and for what use.

Give your clinician’s office your denial letter and the plan’s policy, so their letter answers the plan’s exact reason.

Clinical trials

If you are in an approved clinical trial, federal law says a plan may not deny you the right to take part. It also may not deny or limit coverage of your routine patient costs. The plan does not have to pay for the experimental item itself, or for tests done only to collect data for the study (42 U.S.C. 300gg-8).

How to appeal an experimental or investigational denial

1. Mark your deadline. Find the appeal deadline on the denial letter and put it on your calendar.
2. Ask for the plan’s policy and your file. Request the policy the plan used and a free copy of your claim file (29 CFR 2560.503-1(h)(2)(iii)).
3. Share them with your clinician. Ask for a letter that answers the plan’s reason and cites the evidence that supports the care.
4. Gather your records. Include visit notes, test results, and every treatment you already tried, with dates and results.
5. Ask for urgent review if needed. If waiting could seriously harm your health, ask for an expedited appeal. You can also ask about expedited external review at the same time.
6. Write a short appeal letter. Use the template below and attach everything.
7. Send it and keep proof. Use the method on the denial letter. Save the fax confirmation, mail receipt or portal screenshot.
8. Ask for external review. If the plan upholds the denial, request an external review before that deadline.

Sample appeal letter

[Your name]
[Your address] · [Your phone] · [Your email]

[Date]

[Plan name] — Appeals Department
[Address or fax from your denial letter]

RE: Appeal of "experimental or investigational" denial
Member name: [Name]
Member ID: [Number]
Claim / reference number: [Number]
Service: [Treatment, test or device]
Ordering clinician: [Name, credentials]
Date of denial letter: [Date]

To the Appeals Department:

I am appealing your decision that [service] is "[copy the exact reason]." I believe this care is accepted treatment for my condition and is medically right for me.

My clinician's enclosed letter explains:
- My diagnosis and the treatments I have already tried: [list with dates].
- Why standard options did not work or are not safe for me: [short reason].
- The published evidence and guidelines that support this care: [list].

Your policy, [policy name or number, date], [does not reflect this evidence / does not address my situation] because [short reason].

Enclosed:
- Letter from [clinician]
- Medical records from [dates]
- Copies of the studies or guidelines cited
- Your denial letter and policy

Please reverse the denial. If you do not, please tell me in writing the specific reason, the policy used, the name and credentials of the reviewer, and how to request an external review.

[If urgent:] My clinician believes waiting could seriously harm my health. I request an expedited review.

Sincerely,
[Signature]
[Printed name]

The appeal letter builder can help you fill in the blanks.

Deadlines

Use the appeal deadline calculator to count the days. Self-funded employer plans generally use the federal external review process. Not sure which applies? Try the appeal route wizard.

Costs of external review

• Kentucky: a one-time $25 filing fee, refunded if you win and waivable for financial hardship. The insurer pays for the review itself (KRS 304.17A-623).
• Indiana: the insurer pays all costs of the review (IC 27-8-29-13).

See the Kentucky and Indiana guides for the full state steps. In Indiana, ask your insurer for its external review request form.

Common mistakes to avoid

• Skipping external review. This is the kind of denial outside review is designed for. Don’t stop after the internal appeal.
• Sending studies without context. Ask your clinician to explain how each study applies to you.
• Not checking the policy date. An old policy may miss newer evidence.
• Leaving out what you already tried. Show why standard care is not enough for you.
• Waiting too long. File before the deadline, even if a record is still on the way.

Where to get help

• Kentucky Department of Insurance: (800) 595-6053, Option 1 (in Kentucky), or (502) 564-6034 (KY DOI Division of Consumer Protection)
• Indiana Department of Insurance Consumer Services: (800) 622-4461 or (317) 232-2395 (IDOI Consumer Services)
• Federal external review information: CMS: HHS-Administered Federal External Review