What Is a VA Nexus Letter and Why Do You Need One?

What Is a Nexus Letter?

A nexus letter is a medical opinion from a qualified healthcare provider that establishes a connection ("nexus") between your current medical condition and an event, injury, or exposure during your military service.

It's called a "nexus" letter because it bridges the gap between two facts the VA already knows:

1. You have a current diagnosis
2. Something happened during your service

The nexus letter provides the medical reasoning for why #1 is connected to #2.

The Magic Words

The VA uses a specific legal standard: "at least as likely as not" (meaning 50% or greater probability). Your nexus letter must use this exact language or its equivalent.

Strong: "It is at least as likely as not (50% or greater probability) that the veteran's current lumbar degenerative disc disease is etiologically related to the lumbar strain documented during active duty service."

Weak: "The veteran's back pain could possibly be related to military service." ("Could possibly" doesn't meet the 50% threshold.)

Who Can Write a Nexus Letter?

Any licensed healthcare provider can write a nexus letter:

• Your treating physician (strongest — they know your history)
• A specialist in the relevant field (orthopedist for musculoskeletal, psychiatrist for mental health)
• An independent medical examiner
• A nurse practitioner or physician assistant

Private nexus letters are valid — you don't need to get one from a VA doctor. In fact, getting a private nexus letter is often the single most effective step you can take.

What a Strong Nexus Letter Includes

1. Provider credentials — Name, license, specialty, experience
2. Records reviewed — List of medical records, service records, and other evidence reviewed
3. Current diagnosis — With ICD-10 code
4. In-service event — What happened during service
5. Medical rationale — The scientific/medical reasoning connecting the two (not just "in my opinion")
6. The opinion — Using "at least as likely as not" language
7. Signature and date

Common Nexus Letter Mistakes

• Using weak language ("may be related" instead of "at least as likely as not")
• No medical rationale — just a conclusory opinion without explaining why
• Not reviewing the actual medical records
• Written by a provider with no relevant expertise
• Not addressing alternative causes (the VA will ask "could this be age-related?")