Not All Nexus Letters Are Created Equal — And Your Doctor's Note Probably Isn't One

By Dr. Drew Brennes, DC — The Nexus Letter Doctor

Every day, veterans walk into VA regional offices with a piece of paper from their doctor and believe they have what they need to win their disability claim. The note says something like: "It is my opinion that this veteran's knee condition is related to his military service." One sentence. Signed. Done.

And then they get denied.

What went wrong? The veteran did everything right — they went to their doctor, they asked for a letter, and they submitted it. The problem is that what they submitted was not a nexus letter. It looked like one. It read like one. But under VA law, it was not one.

Understanding this distinction could be the difference between a denied claim and a fully granted rating.

What the VA Actually Requires

The Department of Veterans Affairs does not just need your doctor to say your condition is connected to your service. It needs your doctor to show why.

This requirement comes directly from the federal courts. In Nieves-Rodriguez v. Peake, 22 Vet. App. 295 (2008), the U.S. Court of Appeals for Veterans Claims established that a medical opinion's probative value — meaning its weight in the eyes of the VA adjudicator — is derived not from the mere conclusion alone, but from the reasoning and rationale that supports it.

In plain terms: the opinion is only as strong as the explanation behind it.

The Court made clear that an examiner must do more than simply state a conclusion. The opinion must reflect that the examiner actually reviewed the relevant clinical history, considered the recognized medical literature, and applied both to the veteran's specific facts. Without that foundation, the opinion carries little to no legal weight — and the VA is permitted to disregard it.

The Three Elements Every Nexus Letter Must Address

A proper nexus letter is not a single statement. It is a structured medical-legal document that addresses three distinct elements VA adjudicators are trained to look for:

1. A Current Diagnosis
The condition being claimed must be formally diagnosed, documented under an ICD-10 code, and confirmed by a treating provider. A nexus letter cannot connect a condition to service if the condition has not been clinically established. Without a current diagnosis, there is nothing to connect.

2. An In-Service Event, Injury, or Disease
The letter must identify what happened during military service — a specific incident, a documented exposure, an occupational hazard, or a pattern of activity — that forms the factual basis of the connection. Generalized references to "service" are insufficient.

3. A Nexus — With Rationale and Literature
This is where most doctor's notes fall apart. The nexus itself must be expressed using the VA's legal threshold language: "at least as likely as not" — meaning a probability of 50 percent or greater. But the opinion does not stop there. It must then explain, in clinical terms, why that connection exists. That explanation should reference the recognized pathophysiology of the condition, the documented mechanisms by which service-related exposures or activities produce that condition, and where applicable, the peer-reviewed medical literature that supports that mechanism.

Without all three elements — diagnosis, in-service event, and a nexus with supporting rationale — the document is not a nexus letter. It is a statement of opinion, and a bare statement of opinion is the easiest thing for a VA rater to discount.

What a Doctor's Note Usually Looks Like

Consider these examples. Each is something a veteran might receive from a well-meaning physician and reasonably believe constitutes a nexus letter:

"Based on my treatment of this patient, I believe his lumbar disc disease is related to his military service."

"In my medical opinion, this veteran's hypertension may be connected to his years of service."

"It is possible that this patient's hearing loss developed as a result of noise exposure in the military."

Read each one carefully. Every single one fails the Nieves-Rodriguez standard — and one of them fails before it even starts.

The first offers a belief with no clinical reasoning behind it. Why does the physician believe this? What is the pathophysiologic mechanism? What does the medical literature say about lumbar disc disease in service members? The rater reading this cannot answer those questions from the document, which means the document cannot carry the claim.

The second uses the word "may." Under VA law, "may be connected" does not meet the "at least as likely as not" threshold. "May" expresses possibility, not probability. The VA will read that language and find that the standard has not been met.

The third says "it is possible." Again — possibility is not probability. One of the most common and costly errors in VA nexus opinions is the use of language that falls short of the legal threshold. Words like possible, might, could, may, and cannot rule out are not equivalent to "at least as likely as not." The VA is required to apply the standard literally, and when the language falls short, the claim falls with it.

What a Proper Nexus Letter Actually Contains

A properly prepared nexus letter is a comprehensive medical-legal document. It is not a paragraph. In the most well-developed cases, it is a multi-page document that includes the following:

• A complete review of the record — the examiner identifies and confirms having reviewed the service records, treatment records, C&P exam reports, rating decisions, and any lay statements submitted by the veteran.

• A narrative of the clinical facts — the examiner documents the veteran's current diagnosis, its severity, its progression, and its clinical course in terms that establish the condition as real, ongoing, and documented.

• An articulation of the in-service connection — the examiner identifies the specific service-related event, exposure, or occupational pattern that forms the factual basis of the nexus.

• A stated opinion using the correct legal threshold — the opinion is expressed as "at least as likely as not" (or a stronger formulation such as "more likely than not" or "is caused by"), never using hedging language that falls below that threshold.

• A clinical rationale explaining the mechanism — the examiner explains, in pathophysiologic terms, how the in-service event produced or contributed to the current condition. This is the section that gives the opinion its legal weight.

• Peer-reviewed medical literature — the examiner cites and often quotes from published, peer-reviewed studies that support the stated mechanism. This establishes that the opinion is grounded in accepted medical science, not personal belief.

• A restatement of the opinion — the conclusion is restated clearly, tying the literature, the rationale, and the veteran's specific facts together into a final opinion that the VA adjudicator can follow from start to finish.

Every element works together. Remove any one of them and the document becomes weaker. Remove several and it becomes a doctor's note — which is exactly what most veterans are unknowingly submitting.

Why This Matters More Than Most Veterans Realize

The VA adjudicator reviewing a disability claim is not a physician. They are a rater — a trained government employee who applies a legal framework to the evidence in front of them. They cannot fill in the gaps in a medical opinion. They cannot read between the lines of a vague doctor's note and infer the rationale that should have been stated explicitly.

When a nexus opinion lacks rationale, the rater is left with a conclusion without a foundation. And under Nieves-Rodriguez, they are permitted — and in some cases required — to give that opinion little or no weight in the adjudication.

Meanwhile, if the VA's own contracted examiner provided a negative opinion with a full rationale — even one you disagree with — that documented opinion will outweigh your undeveloped doctor's note every time.

This is why veterans who bring a one-sentence statement to their claim and lose are not necessarily losing because the VA was wrong. They are losing because their evidence, in its current form, does not meet the legal evidentiary standard the VA is required to apply.

The Bottom Line

A nexus letter and a doctor's statement are not the same thing, and the difference is not a technicality. It is the legal foundation on which your claim rests.

Your doctor may be an excellent clinician. They may genuinely believe your condition is service-connected. But believing it and documenting it in a way that meets the VA's evidentiary standard are two different things. A well-meaning physician who writes a two-sentence opinion — however sincerely held — has not given you a nexus letter. They have given you a starting point that still needs to be developed.

If you are preparing a claim or a supplemental claim and you have a doctor's note that you believe supports your case, have it evaluated by someone who understands both the medical and the legal standards the VA applies. Know what you have — and know what you need — before you submit.

It's also worth noting that the legal standards the VA applies are not static. The secondary service connection causation framework was updated in May 2026 — see The VA Changed the Rules on Secondary Claims: What the New 'But For' Standard Means for Your Nexus Letter (2026) to understand how the required opinion language has changed and what a properly prepared secondary nexus letter must now say.

Dr. Drew Brennes, DC is The Nexus Letter Doctor. He specializes in the preparation of medically and legally sufficient nexus letters for veterans pursuing VA disability claims, combining peer-reviewed medical literature with the specific evidentiary standards the VA is required to apply. For a consultation or to learn more, visit nexusletterdoctor.com.