Did You Know?
The magic phrase is 'at least as likely as not.' A doctor doesn't have to be certain your condition was caused by service — they just need to say it's 50% or more likely. That's the VA's threshold.
If your VA claim was denied for 'service connection not established,' a nexus letter is probably the piece of evidence that was missing. It's one of the most powerful tools in the VA claims process — and one of the least talked about.
What Is a Nexus Letter?
A nexus letter is a written statement from a medical professional — MD, DO, PA, or NP — stating that your condition 'is at least as likely as not' related to your military service. That phrasing isn't just suggested language, it's the legal standard the VA uses. You don't need a doctor who can say your condition was definitely caused by service. You just need one willing to say it's 50% or more likely. The letter is typically one to three pages and focuses on connecting your diagnosis to your service history.
What a Good Nexus Letter Includes
- The doctor's qualifications, specialty, and medical license number
- A brief description of your relevant service history and exposures
- Your current diagnosis
- The opinion using 'at least as likely as not' language
- The reasoning — what records were reviewed, what medical literature supports the connection
- Signature and date
Who Can Write One?
Any licensed medical provider can write a nexus letter — it does not have to be a VA doctor. Your primary care physician, a specialist, or your mental health provider can all write one. In practice, private doctors are often more willing than VA doctors, who may feel constrained about making statements outside VA guidelines. If your VA doctor won't write one, ask your private provider.
When Do You Need a Nexus Letter?
- Direct service connection — your condition started or was diagnosed during service
- Secondary service connection — your condition was caused or aggravated by an already-rated condition
- Aggravation claims — a pre-existing condition was made significantly worse by military service
- NOT needed for presumptive conditions — PACT Act and other presumptives are service-connected automatically without a nexus
How to Ask Your Doctor
Be direct. Bring your DD-214, any relevant service records, and a brief summary of your claim. Better yet, bring a draft letter the doctor can review and modify — this takes 10 minutes of their time instead of an hour. Give them the key phrase explicitly: 'The VA standard is at least as likely as not. I just need you to say whether my condition meets that standard based on your medical opinion.' Most doctors are willing once they understand the bar isn't certainty.
The Secondary Condition Multiplier
Secondary claims are one of the most overlooked strategies in VA benefits. If you have a rated condition, any condition caused or worsened by it can be claimed as secondary — and each secondary condition needs its own nexus letter. Common secondary pairs: PTSD connecting to sleep apnea (worth 50%), PTSD connecting to migraines, back pain connecting to radiculopathy in the legs (worth 20% per leg), TBI connecting to depression. Each of these represents hundreds of dollars per month. A nexus letter is what makes the connection official.