Nexus Letters — What They Are and How to Get a Strong One

A nexus letter is a written medical opinion connecting your current condition to your military service (or to another service-connected condition). It's the bridge between "I have this condition" and "this condition is service-connected."

For claims that aren't presumptive — especially those filed years after discharge — the nexus letter is frequently the deciding piece of evidence.

The magic words: "at least as likely as not"

The VA's standard for service connection is "at least as likely as not" — a 50% or greater probability. A strong nexus letter states the provider's opinion in that language and, crucially, explains the medical reasoning behind it. A bare conclusion with no rationale carries little weight.

What a strong nexus letter contains

• •The provider's qualifications and confirmation they reviewed your relevant records.
• •A clear current diagnosis.
• •The in-service event, injury, or exposure (or the service-connected condition, for a secondary claim).
• •The opinion in "at least as likely as not" language.
• •The medical rationale — why, in this provider's expert judgment, the connection exists, ideally referencing the medical literature.

Who can write one

Any qualified medical provider familiar with your condition — your treating physician, a specialist, or an independent provider. It does not have to be a VA doctor.

The part that's easy to miss

A nexus letter only carries clinical weight once a licensed provider has reviewed and signed it. An unsigned draft is just a draft. The reasoning and the signature are what make it evidence — not the formatting.