Doctors decline nexus letters for a reason almost nobody addresses: they fear being dragged into a legal proceeding. They will not be. VA claims are non-adversarial and the opinion is never cross-examined, and saying that up front changes the conversation. The second thing to say: could and possible are wasted words, because the letter has to reach at least as likely as not.
What a nexus letter is and why it carries weight
For direct or secondary service connection, VA usually needs three things: a current diagnosis, an in-service event (or service connected condition for secondary claims), and a medical opinion linking the two. That medical opinion is the nexus letter.
A letter from your treating doctor (the person who has actually examined and managed your care) is one of the most persuasive forms of nexus evidence VA sees. They know your history, they review your records, and their opinion is not subject to cross-examination in a VA proceeding the way an expert witness might be in court. Most doctors do not realize that. Telling them up front lowers the friction.
The exact language VA looks for
The rater is looking for an opinion phrased in one of these two ways:
- "It is at least as likely as not that the veteran's [condition] is related to [service event or service connected condition]."
- "It is more likely than not..."
Under 38 USC 5107(b) and 38 CFR 3.102, the benefit-of-the-doubt rule means that anything 50 percent or better is enough. Make sure that exact phrase appears.
The rater will discount opinions that use weaker hedges ("could," "possible," "may be related to") because those do not meet the 50 percent threshold. The opinion also needs a rationale, the reasoning behind the conclusion. An unsupported opinion gets the same weight as no opinion at all.
A nexus letter template you can hand to your doctor
Fill in the bracketed sections, attach the medical records you want the doctor to review, and bring this to your appointment. If you are working with a VA accredited representative, ask them to review it first.
``` [Your name] [Your address] [Phone, email] [Date]
[Doctor's name and title] [Practice name and address]
Dear Dr. [Last name],
I am writing to ask you for a medical nexus opinion to support my VA disability claim for [condition]. The Department of Veterans Affairs requires a medical opinion linking a current condition to an event or exposure during my military service, or to another service connected condition.
Veteran name: [Full legal name] Date of birth: [DOB] Military service: [Branch, dates, MOS / rate]
Diagnosed condition(s): [List the diagnoses you want the opinion to address.]
The in-service event or service connected condition: [Describe in two or three sentences. Cite service records, prior decisions, or other documentation.]
I have enclosed the following records for your review: - Service treatment records (highlighted) - VA C&P examination report dated [date], if applicable - [List private treatment records, sleep study, imaging, labs] - Lay statements I have submitted, if any
I am asking you to consider the records and address the following question:
Is it AT LEAST AS LIKELY AS NOT (a 50 percent or greater probability) that my current [condition] is related to [the in-service event or service connected condition]?
Please state your opinion using that exact phrase, and please explain the reasoning behind your opinion, including which records you reviewed and which facts you relied on. The rationale matters as much as the conclusion.
If the answer is yes, the VA standard for service connection is satisfied. If the answer is no, please say so plainly and explain why; an honest opinion is still useful to me.
A note for your peace of mind: your written opinion will be submitted to the VA as evidence in a non-adversarial benefits claim. You will not be required to testify and your opinion is not subject to cross-examination in this process.
Thank you for your time. If you have any questions, please contact me at the number above, or my accredited representative, [name and contact].
Sincerely,
[Your signature] [Your printed name] ```
What the doctor's letter should look like when it comes back
A strong nexus letter usually has six pieces. Walk through them with the doctor if you can.
- Identification. Doctor's name, credentials, practice, and contact.
- Records reviewed. A list of the records the doctor actually read. "I reviewed the veteran's service treatment records dated [...], the VA C&P examination of [date], and my own treatment notes from [year] to present."
- Diagnosis. The current diagnosis, with the diagnostic code if known.
- The opinion language. "It is at least as likely as not that [condition] is [caused by / aggravated by / related to] [event or service connected condition]."
- Rationale. A paragraph that ties the records to the conclusion. Mechanism of injury, progression, medical literature, lack of alternative explanation.
- Signature and date.
If the letter is for a secondary claim under 38 CFR 3.310, make sure the opinion addresses both causation (the service connected condition caused the new one) AND aggravation (the service connected condition has made the new one permanently worse than its natural progression). Either one is enough on its own.
When private doctors will not write one
Some private providers do not write nexus letters as a matter of policy. That is their right. Options that still work:
- A different treating doctor in the same practice or a different practice. Specialists who manage the condition (cardiologist, pulmonologist, neurologist, psychiatrist) often will.
- An Independent Medical Opinion (IMO) from a third-party physician. Veterans hire IMO providers across the country. The opinion is usually charged on a flat-fee basis. Quality varies. Ask your VA accredited representative for a list of providers they have actually used.
- VA's own examiner. VA will request a C&P examination and obtain an opinion. The opinion does not always favor the veteran, but you have the right to challenge an unfavorable opinion with a competing private opinion under 38 CFR 3.327 and the AMA review lanes.
Where this comes from
- 38 USC 5107(b), benefit of the doubt
- 38 CFR 3.102, reasonable doubt resolved in favor of the claimant
- 38 CFR 3.159, duty to assist
- 38 CFR 3.303, 3.304, principles of direct service connection
- 38 CFR 3.310, secondary service connection (including aggravation)
- 38 CFR 3.327, examinations
- VA Form 21-4138 and VA Form 21-10210 for the supporting lay evidence
This page is educational only. Work with a VA accredited representative when you can; they can review the nexus letter before it goes into the claim file.
Related on this site
- Lay evidence and personal statements
- Sleep apnea secondary to PTSD
- Building Your Evidence: What VA Looks For and How to Organize It
Common questions
What exact wording does a nexus letter need?
The opinion should say it is "at least as likely as not" (a 50 percent or greater probability) that the condition is related to the in-service event or service connected condition. Under 38 USC 5107(b) and 38 CFR 3.102, anything at 50 percent or better satisfies the benefit of the doubt standard. Hedges like "could" or "may be related to" fall short and get discounted.
Does the letter need more than the magic words?
Yes: a rationale. An unsupported conclusion gets the same weight as no opinion at all. A strong letter lists the records the doctor actually reviewed, states the current diagnosis, gives the opinion in the correct phrasing, and then explains the reasoning: mechanism, progression, literature, and why alternatives are less likely.
Will my own treating doctor's letter carry weight?
Often more than any other source. A treating physician knows your history and manages your care, and the opinion is not subject to cross-examination in VA's non-adversarial process, something many providers do not realize. Telling them that up front, along with handing them a written request and the records to review, lowers the friction considerably.
What should a secondary claim nexus letter address?
Both routes under 38 CFR 3.310: causation (the service connected condition caused the new one) and aggravation (it made the new condition permanently worse than its natural progression). Either one is enough on its own, so the opinion should say which applies.
What if my doctor refuses to write a nexus letter?
Some practices decline as a matter of policy. Alternatives that work: a specialist who manages the condition, an independent medical opinion from a third-party physician (quality varies, so ask an accredited representative for providers they have used), or VA's own examiner, whose unfavorable opinion you can counter with a competing private opinion through the AMA review lanes.