Understanding Nexus Letters

What Is a Nexus Letter?

A nexus letter is a written medical opinion from a qualified healthcare provider that establishes a connection — a "nexus" — between your current medical condition and your military service. That's it. It's not a diagnosis. It's not a treatment plan. It's an opinion, backed by medical reasoning, that says your condition is linked to something that happened during service.

The word "nexus" literally means a connection or link. And in the VA claims world, it's the bridge between what happened to you in uniform and what you're dealing with today.

The Three Elements of Service Connection

Under 38 CFR § 3.303, the VA requires three things to grant service connection for a disability:

• A current medical diagnosis — you have the condition right now, confirmed by a qualified provider
• An in-service event, injury, or illness — something happened during your military service (documented in service treatment records, buddy statements, or your own credible testimony)
• A medical nexus — a qualified medical opinion connecting your current condition to that in-service event

Most veterans can check the first two boxes without much trouble. You've got the diagnosis. You remember the injury or the exposure. But that third element — the nexus — is where claims live or die.

Why Nexus Letters Matter So Much

Here's the reality: the lack of a medical nexus is the #1 reason VA claims get denied. Not missing service records. Not lack of a diagnosis. The missing link between "I have this condition" and "it's because of my service."

The VA denies roughly 30% of initial disability claims. And in a huge portion of those denials, the rating decision letter says something like: "The evidence does not show that your condition is related to your military service." That's the VA telling you they didn't have a nexus opinion — or the one they had wasn't strong enough.

Think about it from the rater's perspective. They're sitting at a desk with your file. They can see you served. They can see you have a diagnosis. But there's nothing in the file — no doctor's opinion, no C&P exam conclusion — that connects A to B. Without that bridge, they can't grant service connection. Even if they personally believe you. The regulation doesn't allow it.

A strong nexus letter changes everything. It gives the rater the medical evidence they need to say "yes." And if you already have a negative C&P exam opinion? A well-written nexus letter from a private provider creates a conflict in the medical evidence — which triggers the benefit of the doubt doctrine under 38 CFR § 3.102. When the evidence is roughly equal for and against, the veteran wins.

What Makes a Strong Nexus Letter

Not all nexus letters are created equal. I've seen letters that are one paragraph long with zero reasoning get completely ignored by the VA. And I've seen detailed, well-sourced letters flip a denial into an approval on appeal. The difference comes down to three things.

1. The Magic Phrase

The VA uses a specific standard of proof called "at least as likely as not" — meaning there's a 50% or greater probability that your condition is related to service. This is the exact language your nexus letter needs to use. Not "could be related." Not "might possibly be connected." Not "cannot be ruled out."

Here's what a strong opinion looks like:

And here's what a weak opinion looks like:

See the difference? The first one is specific, uses the correct legal standard, and references actual service events. The second one is vague, speculative, and gives the rater nothing to work with.

2. Medical Rationale

The opinion alone isn't enough. The VA wants to know why the doctor reached that conclusion. This is the rationale — the medical reasoning that supports the opinion. It should reference medical literature, the veteran's specific history, and the known pathology of the condition.

A strong rationale might read: "Repetitive axial loading on the spine — consistent with the veteran's documented duties as an infantry paratrooper including 47 recorded jumps — is a well-established risk factor for accelerated lumbar disc degeneration in peer-reviewed orthopedic literature (see Smith et al., Journal of Spinal Disorders, 2018). The veteran's MRI findings are consistent with this mechanism of injury."

That's a rationale that a VA rater can hang their hat on. It explains the medical logic and cites evidence.

3. Citation of Service Records

The best nexus letters show that the provider actually reviewed the veteran's service treatment records (STRs), military personnel records, and any relevant post-service medical records. If the doctor references specific dates, specific incidents, and specific findings from those records, it tells the rater this isn't a rubber-stamp opinion — the provider did their homework.

Who Can Write a Nexus Letter

Any competent medical professional can write a nexus letter. That includes:

• Medical Doctors (MDs) and Doctors of Osteopathic Medicine (DOs)
• Nurse Practitioners (NPs)
• Physician Assistants (PAs)
• Psychologists (PhDs/PsyDs) — for mental health conditions
• Audiologists — for hearing loss and tinnitus claims

The VA doesn't have a rule saying "only an MD's opinion counts." But let's be real — a specialist's opinion carries more weight than a generalist's. An orthopedic surgeon writing about your knee is more persuasive than a family practice NP writing about your knee. A psychiatrist's opinion on PTSD hits harder than an internist's. The VA weighs medical opinions based on the provider's expertise relative to the condition.

Private Doctors vs. VA Doctors

Can your VA doctor write you a nexus letter? Technically, yes. In practice? Good luck. Most VA providers won't do it. Some say it's a conflict of interest (it isn't). Others say they're not allowed (they are). And some just don't want to get involved in the claims process.

But here's what VA doctors will do: document your symptoms, provide a diagnosis, and note your reported history in your treatment records. And those treatment notes? They're evidence too. A VA doctor writing "patient reports knee pain since parachute jumps in service" in your medical record is a building block — even if it's not a formal nexus letter.

For the actual nexus letter, most veterans end up going to a private provider. And that's fine. The VA gives equal weight to private medical opinions as long as they're well-reasoned and from a qualified source.

What a Nexus Letter Should Include

Every strong nexus letter follows a structure. It doesn't need to be fancy — no letterhead required, no specific format mandated by the VA. But it needs to cover these elements:

Essential Elements

• Provider's credentials — full name, title, license number, and specialty. The rater needs to confirm this is a qualified professional.
• Veteran's identifying information — name, date of birth, and last four of SSN or VA file number
• Records reviewed — list every document the provider examined. Service treatment records, VA medical records, private treatment records, imaging studies, buddy statements. Be specific.
• Current diagnosis — the specific condition, using the accepted medical terminology and diagnostic criteria (ICD-10 codes are a nice touch)
• Relevant service history — what happened during service that's connected to the condition. Dates, duties, incidents, exposures.
• The nexus opinion — the clear, unambiguous statement using "at least as likely as not" language
• Medical rationale — the detailed reasoning explaining why the provider reached their conclusion. This is the heart of the letter.
• Signature, date, and contact information — makes it a formal medical document

A solid nexus letter is usually 1–3 pages. Not because there's a page requirement, but because covering all these elements with adequate detail naturally takes that space. If your letter is three sentences long, something's missing.

Common Mistakes That Sink Nexus Letters

This is the single biggest area where I see veterans lose winnable claims. They have a nexus letter. They submitted it. And it still didn't work. Here's why.

1. Vague or Speculative Language

"The veteran's condition may be related to service." That word — "may" — killed the letter. The VA reads speculative language as a negative opinion. If the doctor isn't willing to commit to "at least as likely as not," the rater treats it as if the doctor doesn't actually believe there's a connection. Words like "possibly," "could be," "might," and "cannot rule out" all fall below the VA's standard of proof.

2. No Medical Rationale

"It is my opinion that the veteran's hypertension is at least as likely as not related to military service." Full stop. No explanation. No reasoning. This is a bare conclusion, and the VA is well within its rights to give it zero weight. The Board of Veterans' Appeals has thrown out thousands of nexus opinions for exactly this reason — an opinion without rationale is not probative evidence.

3. Using the Wrong Standard

Some doctors write nexus letters using a "more probable than not" or "reasonable medical certainty" standard. Those are legal standards from personal injury cases, not VA claims. The VA's standard is lower and more veteran-friendly: "at least as likely as not." That's 50/50. Your doctor doesn't need to say it's definite — just that it's as likely as not. Make sure they know this before they write the letter.

4. Not Reviewing the Actual Records

A nexus letter that says "based on the veteran's self-reported history" without referencing any actual records is weak. The VA gives more weight to opinions based on a review of the full medical record — not just what the veteran told the doctor in a 15-minute appointment. If your provider didn't review your STRs, your VA records, and your post-service treatment history, the letter has a credibility problem.

5. Generic, Cookie-Cutter Letters

VA raters see hundreds of nexus letters. They know what a template looks like. If your letter reads like a fill-in-the-blank form where someone just swapped in your name and condition, it's going to get discounted. The letter needs to be specific to you — your service, your records, your medical history. Generic doesn't cut it.

How to Get a Nexus Letter

You've got a few options, and the right one depends on your situation, your budget, and who's already treating you.

Ask Your Treating Physician

If you have a private doctor who's been treating your condition, start there. They already know your medical history. They've seen your symptoms firsthand. And their opinion carries weight because they have a longitudinal treatment relationship with you — they're not just doing a one-time review.

The challenge? Most civilian doctors don't know what a nexus letter is. They've never heard the phrase "at least as likely as not." They don't know about 38 CFR § 3.303. You'll need to educate them. Bring them a clear explanation of what you need, the specific language to use, and — ideally — a sample letter they can reference. Don't hand them a completed letter to sign. Give them the framework and let them write it in their own clinical voice.

Independent Medical Opinions (IMOs)

If your treating doctor can't or won't write the letter, your next option is an independent medical opinion from a provider who specializes in VA nexus evaluations. These are doctors — often veterans themselves — who understand the VA system, know the evidentiary standards, and have experience writing opinions that hold up under scrutiny.

An IMO provider will typically review your records, conduct an examination (in person or via telehealth), and produce a detailed letter with the proper language and rationale. The quality is generally higher because this is what they do.

Telehealth Options

You don't need to be in the same room as the doctor. The VA accepts nexus letters based on telehealth examinations — especially since the pandemic normalized virtual medical evaluations across the system. This opens up access to specialists nationwide. If the best doctor for your sleep apnea nexus is in Texas and you're in Maine, a telehealth evaluation works.

But make sure the provider still reviews your full records. A telehealth nexus evaluation should be just as thorough as an in-person one. If someone offers to write you a nexus letter based on a 10-minute phone call with no record review, walk away. That letter won't survive VA scrutiny.

Nexus Letters for Secondary Conditions

Secondary service connection is one of the most underused pathways in the VA claims system. Under 38 CFR § 3.310, you can get service connection for a condition that was caused by or aggravated by an already service-connected disability. And the nexus letter for a secondary claim works a little differently.

Instead of linking your condition directly to an in-service event, the nexus opinion connects your new condition (Condition B) to your existing service-connected condition (Condition A). The in-service event is already established — you just need to build the medical bridge one step further.

Common Secondary Connections

• Sleep apnea secondary to PTSD (PTSD disrupts sleep architecture)
• Depression or anxiety secondary to chronic pain conditions
• Radiculopathy secondary to degenerative disc disease
• GERD secondary to medications for service-connected conditions
• Erectile dysfunction secondary to PTSD medications or diabetes
• Hypertension secondary to PTSD or kidney conditions

The nexus opinion for a secondary claim should read something like:

Notice the two prongs: "proximately due to" (causation) and "chronically aggravated by" (aggravation). Including both gives the rater two bases for granting — if they can't find direct causation, aggravation is the fallback. And aggravation claims under § 3.310(b) are powerful because you only need to show the service-connected condition made the secondary condition worse beyond its natural progression.

What Nexus Letters Cost

Let's talk money. Nexus letters aren't free — and you should be skeptical of anyone offering them for nothing.

Typical Price Ranges

• Your own treating physician: $0–$250. Some doctors will write it as part of your care. Others charge a records review fee.
• IMO providers / nexus specialists: $500–$1,500 per letter. Includes record review, examination (in-person or telehealth), and the written opinion.
• Complex cases or specialists: $1,500–$2,500+. If you need a cardiologist, neurologist, or toxicologist for an unusual claim, expect to pay more.

Is it worth it? Run the numbers. A 30% disability rating is worth roughly $524/month tax-free in 2024. That's $6,288 a year. Over a lifetime, we're talking hundreds of thousands of dollars in tax-free benefits. A $1,000 nexus letter that turns a denial into an approval is one of the best investments you'll ever make.

Why Free Isn't Always Better

I get it — veterans shouldn't have to pay for something they've earned. And some VSOs and nonprofits do connect veterans with providers who'll write nexus letters at no cost. But free nexus letters are often the weakest ones. The provider may not have time for a thorough record review. The rationale might be thin. The language might miss the mark. And a weak nexus letter can actually hurt your claim if the C&P examiner picks it apart.

That doesn't mean every paid letter is good or every free letter is bad. But you generally get what you pay for. Look at the quality of the rationale, not the price tag.

Frequently Asked Questions