Can You Write Medical Necessity Letters?

Yes. Ask Dr. Hu can write medical necessity letters when the requested treatment, service, medication, test, device, or accommodation is medically appropriate and can be supported by the patient's medical history, evaluation, and available clinical evidence.

A letter of medical necessity is more than a doctor's note. It is a clinical document explaining why a particular medical service or intervention is appropriate for an individual patient.

Depending on the request, the physician may need to review your medical records, diagnosis, previous treatments, test results, symptoms, functional limitations, and the specific requirements of the organization requesting the letter.

If you need a medical necessity letter, you can learn more about our Medical Documentation services or visit the Medical Documentation Resource Center.

What Is a Medical Necessity Letter?

A medical necessity letter is a written clinical explanation supporting why a particular medical service, treatment, medication, test, device, or other intervention is appropriate for a patient's condition.

These letters are often requested when another organization needs additional clinical information before deciding whether to approve, authorize, reimburse, or otherwise accept a medical request.

A medical necessity letter may be requested by:

• A health insurance company

• A pharmacy benefit manager

• A medical equipment supplier

• An employer or benefits administrator

• A government program

• Another healthcare organization

• Another entity reviewing a medically related request

The exact requirements vary depending on who will receive the letter.

For insurance-related requests, medical necessity is particularly important because health plans frequently use medical criteria and clinical documentation when determining whether a service is eligible for coverage. The Centers for Medicare & Medicaid Services, for example, evaluates whether covered services meet applicable requirements for being reasonable and necessary.

What Can a Medical Necessity Letter Be Used For?

Medical necessity letters may be requested for many different reasons.

Examples can include supporting the medical rationale for:

Medications

An insurer may require additional information explaining why a particular medication is appropriate, especially when preferred alternatives have previously been attempted or are not suitable.

Medical Procedures or Treatments

A physician may be asked to explain why a proposed treatment or procedure is appropriate based on the patient's diagnosis, symptoms, examination findings, previous treatments, and clinical circumstances.

Diagnostic Testing

Certain laboratory tests, imaging studies, or other diagnostic procedures may require documentation explaining why testing is clinically indicated.

Medical Equipment or Devices

Patients may need supporting documentation for durable medical equipment, mobility devices, braces, monitoring equipment, or other medically necessary supplies.

Rehabilitation or Therapy

Physical therapy, occupational therapy, rehabilitation programs, or other therapeutic services may sometimes require documentation supporting the proposed frequency, duration, or medical rationale.

Other Healthcare Services

A medical necessity letter may also apply to services that do not fit neatly into one category. The important question is whether there is a legitimate medical reason for the request that can be supported through appropriate clinical documentation.

What Does a Medical Necessity Letter Usually Include?

The contents of the letter depend on the request, but a physician may include information such as:

• The patient's relevant medical condition or diagnosis

• Pertinent symptoms or functional limitations

• Relevant medical history

• Previous treatments or therapies

• Treatment response or reasons alternatives may not be appropriate

• Relevant examination findings

• Laboratory, imaging, or other test results

• The treatment, service, medication, or device being requested

• The clinical reasoning supporting the request

• Anticipated medical or functional benefit

• Relevant supporting records or medical evidence

The goal is not simply to state that something is medically necessary. A strong medical necessity letter explains why the request is reasonable for the particular patient based on the available clinical information.

Do I Need Medical Records?

Often, yes.

The amount of documentation needed depends on what you are requesting and the requirements of the organization reviewing the letter.

Useful records may include:

• Recent physician notes

• Specialist records

• Hospital or emergency department records

• Laboratory results

• Imaging reports

• Medication history

• Physical therapy records

• Previous treatment records

• Prior authorization or denial notices

• Insurance correspondence

• Forms or instructions from the requesting organization

If you already have the relevant records, providing them before your appointment can make the review process more efficient.

Patients generally have the right to obtain copies of their medical records from covered healthcare providers and health plans, subject to certain limitations. The U.S. Department of Health and Human Services provides additional information about accessing your medical records.

Do I Need an Appointment Before a Letter Can Be Written?

In many cases, yes.

A physician needs enough clinical information to responsibly support the statements contained in a medical necessity letter.

Depending on the situation, this may require:

• Reviewing your medical history

• Reviewing outside medical records

• Discussing your current symptoms and treatment

• Evaluating previous therapies

• Reviewing diagnostic testing

• Performing an appropriate medical evaluation

• Clarifying exactly what the receiving organization is requesting

Some documentation requests can be addressed through a virtual appointment, while others may require an in-person examination or additional testing.

The appropriate process depends on the nature of the request.

Can You Write a Letter for Something Another Doctor Recommended?

Potentially.

If another physician or specialist has recommended a treatment, medication, procedure, test, or device, those records can be very helpful.

However, signing a medical necessity letter means that the physician writing the letter must be able to independently support the statements being made.

A recommendation from another clinician therefore does not automatically mean that a new physician can sign the requested documentation without reviewing the underlying medical information.

Providing the specialist's consultation notes, diagnostic findings, treatment recommendations, and other relevant records may help establish the necessary clinical basis.

Can You Write a Medical Necessity Letter Without Supporting Documentation?

Not always.

Medical documentation should accurately reflect the information available to the physician.

If there is insufficient medical evidence to support a request, additional records, evaluation, or testing may be necessary before a letter can be completed.

In some cases, the physician may determine that the requested wording cannot be medically supported.

When that happens, the appropriate approach may be to modify the documentation so that it accurately reflects the available evidence—or decline to make a statement that cannot be clinically substantiated.

This protects both the patient and the integrity of the medical record.

Can You Guarantee That My Insurance Company Will Approve the Request?

No.

A medical necessity letter provides clinical support for a request, but it does not control the final decision made by an insurance company, employer, government agency, or other organization.

Different organizations may apply different:

• Coverage policies

• Eligibility requirements

• Medical criteria

• Prior authorization rules

• Documentation requirements

• Contract exclusions

Even a medically reasonable request can be denied under a particular benefit plan or policy.

If an insurance request is denied, review the denial carefully. It may explain what information is missing, why the request did not meet the plan's criteria, and whether an appeal is available. The U.S. Department of Health and Human Services provides additional information about health insurance appeals and external review rights.

Is a Medical Necessity Letter the Same as Prior Authorization?

Not necessarily.

Prior authorization is a process through which an insurer requires approval before certain medications, treatments, procedures, or services are covered.

A medical necessity letter is documentation that may be submitted as part of that process.

Depending on the situation, an insurer may request:

• A standardized prior authorization form

• Medical records

• Diagnostic test results

• Treatment history

• A physician statement

• A letter of medical necessity

• Additional documentation after an initial denial

A letter alone may therefore not satisfy every requirement.

If you received paperwork from your insurance company or another organization, bring or upload the entire request or denial notice, not just the page requesting a physician signature.

What Should I Bring to a Medical Necessity Letter Appointment?

To help your physician evaluate the request efficiently, provide as much relevant information as possible.

Helpful items include:

• The form or written request

• Insurance denial or prior authorization notice

• Relevant medical records

• Specialist recommendations

• Laboratory or imaging results

• Current medication list

• Previous treatments and outcomes

• Details about the treatment, medication, test, or device being requested

• Any deadline for submitting the documentation

• Instructions for where the completed documentation should be sent

Whenever possible, obtain these documents before your appointment.

You can learn more about the overall process in our Medical Documentation Resource Center.

How Long Does It Take to Write a Medical Necessity Letter?

The amount of time required depends on the complexity of the request.

A relatively straightforward letter based on records already available may require much less review than a complex request involving years of medical history, multiple specialists, previous treatment failures, or extensive insurance requirements.

Additional time may also be necessary if records must be obtained from other healthcare providers.

Providing organized records and the requesting organization's exact requirements from the beginning can help reduce unnecessary delays.

How Much Does a Medical Necessity Letter Cost?

The cost depends on the amount of physician time and documentation required.

Medical necessity letters can vary substantially in complexity. Some require a relatively short review and letter, while others involve extensive medical-record review, research, forms, supporting documentation, or communication with another organization.

For current information about medical documentation services, visit our Medical Documentation page.

Can a Physician Decline to Write a Medical Necessity Letter?

Yes.

A physician may decline a request if there is not enough clinical information to support it or if the requested statement does not accurately reflect the physician's medical assessment.

For example, additional evaluation may be needed when:

• The physician has not evaluated the underlying condition

• Important medical records are unavailable

• The requested treatment has not been adequately assessed

• The requested wording exceeds what the evidence supports

• An examination or diagnostic testing is needed

• The request asks the physician to certify information outside the physician's ability to verify

Medical documentation should reflect an independent clinical assessment—not simply reproduce wording requested by a patient, insurer, employer, attorney, or another organization.

Can Ask Dr. Hu Help With My Medical Necessity Letter?

Yes, when there is an appropriate medical basis for the request.

The process generally begins by determining:

1. What documentation is being requested

2. Who will receive the documentation

3. What medical issue the letter concerns

4. What supporting records are available

5. Whether additional evaluation is necessary

6. Whether the requested statements can be medically supported

After reviewing the available information, the physician can determine what documentation can appropriately be provided.

For more information, visit Medical Documentation at Ask Dr. Hu or contact Ask Dr. Hu to discuss your documentation request.

Medical Review & Editorial Standards

This article was written for patient education and reflects general principles used when evaluating requests for medical documentation. Medical necessity decisions are individualized and may depend on a patient's diagnosis, medical history, examination, previous treatment, clinical evidence, and the requirements of the organization reviewing the request.

Ask Dr. Hu does not guarantee that a particular letter can be written or that a third party will approve a request. Documentation is provided only when the requested statements can be reasonably supported by the available medical information and the physician's independent clinical assessment.

Authoritative resources used in developing and reviewing this information include:

• Centers for Medicare & Medicaid Services — Medicare Coverage Determination Process

• Centers for Medicare & Medicaid Services — Documentation Matters

• U.S. Department of Health and Human Services — Your Medical Records

• U.S. Department of Health and Human Services — Health Insurance Appeals

Last reviewed: August 2026

About the Author

Dr. YiQiu Hu, NMD is an Arizona-licensed naturopathic physician and the founder of Ask Dr. Hu, a physician-led medical practice serving patients throughout Arizona. His clinical work includes personalized medical care, preventive health, medical documentation, integrative pain management, hormone therapy, medical weight management, and other individualized healthcare services.

Through Ask Dr. Hu, patients can receive physician evaluation and medical documentation for appropriate work, school, disability, insurance, and other medically related requests when supported by the patient's clinical circumstances.

Learn more about Ask Dr. Hu or explore our Medical Documentation services.

This article is for general educational purposes and does not guarantee that a particular documentation request will be medically appropriate, accepted by a third party, or covered by an insurance plan.