A nexus letter is a medical opinion from a qualified healthcare provider stating that a veteran's current condition is connected to their military service. The term "nexus" means link or connection. In VA claims, the nexus opinion is often the element that determines whether a claim is granted or denied.
The legal standard for a favorable nexus is "at least as likely as not" — meaning there is a 50% or greater probability that the condition is related to service. The opinion does not need to state certainty, only that the connection is at least as probable as not.
A strong nexus letter contains: the provider's credentials and qualifications, a statement that the provider reviewed the veteran's medical records and service history, a description of the veteran's current condition and diagnosis, identification of the relevant in-service event or exposure, a clear opinion using the "at least as likely as not" language, and a detailed medical rationale explaining why the connection exists. The rationale is the most important part — a bare opinion without explanation carries little weight.
Common weaknesses in nexus letters include: using language weaker than the legal standard ("it is possible" or "it could be related" is not strong enough), failing to review the actual medical records, not providing a medical rationale, and making conclusory statements without supporting reasoning.
You can obtain a nexus letter from your own private physician, a medical expert who reviews your records, or through companies that connect veterans with providers experienced in VA claims. The VA must consider private nexus opinions and cannot dismiss them without explanation. If the VA's C&P examiner provides a negative nexus and you submit a positive private nexus, the VA must weigh both opinions and explain which it finds more persuasive and why.
A well-written nexus letter from a qualified provider who reviewed the records and provided detailed reasoning is one of the most powerful pieces of evidence in a VA claim.
Note: This article references sections of the VA's M21-1 Adjudication Procedures Manual. The VA periodically reorganizes the M21-1 and section numbers may have changed since this article was written. For the most current section references, visit the VA's public M21-1 Web Automated Reference Material System (WARMS).