A nexus letter is a written medical opinion connecting your current diagnosed condition to your service (or, for a secondary claim, to a service-connected condition). It supplies the link — the third element of service connection and the one most denied claims are missing. A strong one uses VA's "at least as likely as not" standard and explains the reasoning, not just the conclusion.
Straight talk first
Most claims don't get denied because the veteran isn't hurt. They get denied because nobody connected the dots in writing that VA accepts. You can have a rock-solid diagnosis and clear proof something happened in service, and still lose — because the link between them was never medically stated. That link is the nexus, and a nexus letter is how you put it in front of the rater. Get this piece right and a stalled claim comes alive.
This builds on the three elements covered in how to file your own claim.
What VA's standard actually is
VA doesn't require certainty. The standard is "at least as likely as not" — meaning a 50% or greater probability that your condition is connected to service. That's a deliberately low bar, and the benefit of the doubt goes to you when the evidence is balanced. A good nexus letter states that standard in plain terms and then backs it up.
What a strong nexus letter contains
The conclusion alone ("these are related") is weak. A persuasive nexus letter shows its work:
- The provider's qualifications — who they are and why they're competent to opine on this condition.
- What they reviewed — your service records, medical history, and relevant evidence (a review of the file carries more weight than a one-visit impression).
- The opinion, in the standard language — that the condition is "at least as likely as not" related to service.
- The medical rationale — why: the mechanism, the timeline, the supporting literature or clinical reasoning. This is the part VA weighs most.
A letter that says "it is at least as likely as not" with no reasoning is far weaker than one that explains the medical "because."
Who writes it
A qualified medical professional — your treating physician, a specialist, or a private provider who reviews your records for the purpose. Match the expertise to the condition. Note that a nexus letter is often confused with a DBQ — the DBQ documents the severity of a condition for rating, while the nexus letter addresses causation. Many strong claims use both.
When you may not need one
- Presumptive conditions — VA presumes the link, so no nexus is required.
- Clear C&P opinions — sometimes the C&P examiner provides a favorable nexus opinion themselves.
- Obvious in-service onset — where the records plainly show the condition began in service.
For everything else — especially secondary claims where the connection isn't self-evident — a strong private nexus letter is often the lever that wins.
A note on cost and honesty
You may pay a provider to write one; that's allowed, and you're responsible for the fee. Be wary of anyone promising a guaranteed outcome from a letter — no one can promise that, and VA weighs the quality of the opinion, not the fact that you have one. Pointman is education-only and not VA-accredited; we teach you what a strong nexus looks like so you can have an informed conversation with a provider.
Key takeaways
- A nexus letter is the medical opinion linking your condition to service — the most commonly missing element.
- VA's standard is "at least as likely as not" (≥50%); strong letters state it and explain the reasoning.
- It should show the provider's qualifications, records reviewed, opinion, and rationale.
- Not needed for presumptives; distinct from a DBQ (severity vs. causation).
Frequently asked questions
- What is a nexus letter?
- A nexus letter is a written medical opinion from a qualified provider connecting your current diagnosed condition to your military service (or to a service-connected condition, for a secondary claim). It supplies the 'link' element of service connection — the piece most denied claims are missing.
- What's the 'at least as likely as not' standard?
- VA's standard of proof is whether it's 'at least as likely as not' (a 50 percent or greater probability) that your condition is connected to service. A strong nexus letter uses that language and explains the medical reasoning behind it — not just the conclusion.
- Who can write a nexus letter?
- A qualified medical professional — your treating physician, a specialist, or a private provider who reviews your records. It should be someone whose expertise fits the condition. VA weighs the opinion partly on the provider's qualifications and how thoroughly they reviewed your history.
- Do I always need a nexus letter?
- Not always. Presumptive conditions don't require proving a nexus, and sometimes the C&P examiner's own opinion supplies it. But for many direct and secondary claims — especially where the connection isn't obvious — a strong private nexus letter is the difference-maker.
Sources
- 38 CFR 3.303 — principles relating to service connection: https://www.law.cornell.edu/cfr/text/38/3.303
- 38 CFR 3.102 — reasonable doubt ("at least as likely as not"): https://www.law.cornell.edu/cfr/text/38/3.102
- VA — Evidence needed for your disability claim: https://www.va.gov/disability/how-to-file-claim/evidence-needed/
- VA — Private medical evidence (DBQs): https://www.benefits.va.gov/compensation/dbq_disabilityexams.asp
