38 CFR 3.310: Secondary Claims, Aggravation, and Evidence

38 CFR 3.310 lets you claim VA disability compensation for a condition that was caused by, or made worse by, a disability you are already service-connected for. Subsection (a) covers direct causation, where the service-connected disability produced a new condition. Subsection (b) covers aggravation, where the service-connected disability worsened a condition you already had. Once granted, the secondary condition is treated as part of your service-connected disability for rating purposes, so your combined rating reflects the full downstream impact of your service.¹

Direct Causation Under 3.310(a)

The rule under subsection (a) is that any disability “proximately due to or the result of” a service-connected disease or injury qualifies for service connection on its own.¹ The test is causation: without the primary service-connected disability, the secondary condition would not exist.

A common example is a veteran with a service-connected knee injury who develops chronic lower back pain after years of an uneven gait. The back condition exists because the knee changed how the veteran moves. That causal chain is what the VA looks for.

The secondary condition must be a diagnosed disability, not just a symptom. If a physician can identify a specific condition with its own diagnostic code, the VA has something to rate. Vague pain complaints without a corresponding diagnosis rarely survive adjudication.

Aggravation Under 3.310(b)

Not every secondary claim involves a brand-new condition. Under subsection (b), any increase in severity of a non-service-connected condition caused by a service-connected disability, and not due to the natural progression of the disease, qualifies for service connection.²

The distinction that matters is between the natural course of a disease and the extra harm caused by your service-connected disability. Degenerative disc disease that would have worsened on its own over the next decade is not compensable. If your service-connected foot injury forces an abnormal gait that accelerates the disc degeneration beyond that natural rate, the difference is compensable.

The Baseline Calculation

Aggravation claims involve math that trips up a lot of veterans. The VA must establish a baseline level of severity for the non-service-connected condition before granting benefits. That baseline comes from medical evidence created either before the aggravation began or from the earliest records available between the onset of aggravation and the current severity level.² The VA then determines the current severity, subtracts the baseline, subtracts any worsening attributable to natural progression, and compensates only the remaining increase.

Without records showing what the condition looked like before it got worse, the VA struggles to set the baseline and the claim stalls. Old treatment records, prior imaging, and primary care notes documenting a mild condition before it became severe all work as baseline evidence. Gather them before you file.

Conditions Caused by Prescribed Medication

A pathway veterans frequently overlook: secondary connection for conditions caused by medication prescribed for a service-connected disability. If you take NSAIDs for a service-connected orthopedic injury and develop gastroesophageal reflux disease as a result, that digestive condition can qualify. The Board of Veterans’ Appeals has granted claims on that theory, relying on medical literature identifying NSAIDs as a causal factor for GERD along with treatment records showing long-term use.³

The same logic reaches other side effects: sleep medications causing cognitive issues, psychiatric drugs causing weight gain or metabolic changes, opioid painkillers causing gastrointestinal problems. The evidence requirements are the same as any other secondary claim. You need a current diagnosis, proof you take the medication for a service-connected disability, and a medical opinion linking the medication to the new condition. Long duration of use strengthens the causal argument.

Evidence That Wins Secondary Claims

A secondary claim lives or dies on medical evidence. You need three things: a current diagnosis, treatment records that connect the two conditions, and a medical opinion tying them together.

The Nexus Letter

The nexus letter is the most important document in the file. It is a written opinion from a qualified medical professional stating that your secondary condition is “at least as likely as not” caused or aggravated by your service-connected disability.⁴ That phrase is not casual language. It sets the bar at 50% probability, which triggers the benefit-of-the-doubt rule: under 38 CFR 3.102, when evidence for and against a claim is roughly equal, the VA resolves the doubt in your favor.⁵

A strong letter does more than state a conclusion. It explains why the primary condition causes or worsens the secondary one, cites medical literature that supports the connection, and points to your specific treatment history. A letter that says “I believe the conditions are related” without explaining the mechanism is easy for a VA examiner to dismiss. Private nexus letters typically run between $650 and $4,500 depending on complexity and specialty, but a well-written one often prevents an appeal that would take far longer.

The Disability Benefits Questionnaire

A Disability Benefits Questionnaire is a standardized VA form that documents the diagnosis, symptoms, and functional limitations of a specific condition in a format raters already know how to read. Your private doctor can complete one. Pairing a DBQ with a nexus letter gives the rater both the clinical picture and the causation opinion. The DBQ answers “what is wrong,” the nexus letter answers “why it is connected,” and together they often make a claim decision-ready without another examination.

Supporting Records

Include every relevant treatment record. For aggravation claims especially, records showing the condition’s severity before it worsened are essential to establish the baseline. Lab results, imaging, range-of-motion measurements, and treatment notes covering the development of the secondary condition all strengthen the file. Care received outside the VA system is your responsibility to gather and submit.

Filing the Claim

File a secondary claim using VA Form 21-526EZ, the same form used for all disability compensation claims.⁶ Identify the new condition on the form and specify that you are claiming it as secondary to your existing service-connected disability. Include the dates and locations of treatment.

You can file through the VA.gov online portal, which usually produces faster confirmation, or mail your documents to:

Department of Veterans Affairs
Claims Intake Center
PO Box 4444
Janesville, WI 53547-4444⁷

Protect Your Effective Date

Before your evidence is complete, submit an Intent to File using VA Form 21-0966. This sets a potential start date for your benefits. If the claim is later approved, you may receive retroactive payments back to the date the intent to file was processed rather than the date you submitted the completed claim.⁸ You have one year from that date to file the full claim. Miss the window and you lose the earlier effective date, which can mean thousands of dollars in back pay.

The Compensation and Pension Exam

After the VA receives your claim, it may schedule a Compensation and Pension exam with a VA-contracted medical professional. The examiner reviews your records, evaluates you in person, and provides an opinion on whether the secondary condition is connected to the primary disability. This opinion carries significant weight with the rater, sometimes more than a private nexus letter, because the VA treats its own examiners as independent evaluators.

Missing the exam has real consequences. Under 38 CFR 3.655, if you fail to attend an exam scheduled for an original compensation claim without good cause, the VA decides the claim based on whatever evidence is already in the file, which usually means a denial or a lower rating. For supplemental claims, reopened claims, or claims for increased ratings, the claim is denied outright.⁹ Good cause includes hospitalization, the death of an immediate family member, or similar emergencies. If you cannot make the appointment, contact the VA before the date to reschedule.

At the exam, be specific about how the secondary condition affects you and how it relates to the primary disability. The examiner is writing a report a rater will use, so concrete descriptions of symptoms and functional limitations help more than general statements about pain. If you have a nexus letter from a private physician, the examiner will likely address whether they agree with its conclusions.

How Your Rating Actually Changes

Adding a secondary condition does not mean two ratings get added together. Under 38 CFR 4.25, the VA uses a combined ratings formula that accounts for each additional disability affecting a smaller share of your remaining capacity.¹⁰ If your primary disability is rated at 50% and the secondary is rated at 30%, you do not get 80%. The VA starts with the 50%, treats the remaining capacity as 50%, applies 30% to that (15%), and adds it back for 65%, which rounds to 70%.

The result is always lower than straight addition, but small individual ratings still matter because crossing a threshold from 60% to 70% or from 90% to 100% can add hundreds of dollars per month.

The Pyramiding Rule

When a secondary condition is added, the VA checks whether its symptoms are genuinely separate from what is already being compensated. Under 38 CFR 4.14, the same set of symptoms cannot be rated under two different diagnoses.¹¹ This catches veterans off guard when a secondary claim is granted but rated at zero percent because symptoms overlap with the primary condition.

The most common overlap involves PTSD and traumatic brain injury, where difficulty sleeping, concentrating, and managing mood appear in both diagnoses. If the VA cannot separate which symptoms come from which condition, it assigns a single rating under whichever produces the higher evaluation. The same problem arises with musculoskeletal conditions affecting the same body region: if the primary rating already reflects limited mobility of the knee, a secondary back condition also limited by mobility will not be double-counted.

Where pyramiding works in your favor is when the secondary condition produces clearly distinct symptoms. A service-connected knee injury causing secondary radiculopathy involves two different body systems and two different symptom sets, so both can be separately rated. Frame the claim around what is unique to the secondary condition.

If the Claim Is Denied

A denied secondary claim is not the end. You have one year from the date on the decision letter to pursue one of three review options.¹²

A Supplemental Claim is the right lane if you have new and relevant evidence the VA has not considered, such as a stronger nexus letter or new treatment records. The processing goal is about 125 days.
A Higher-Level Review is the right lane if you believe the rater made an error on the evidence already in the file. A more senior reviewer looks at the same record but cannot consider new evidence. The processing goal is also about 125 days.
A Board Appeal sends the case to a Veterans Law Judge. You can request direct review with no new evidence, submit additional evidence, or request a hearing. Direct reviews have a goal of about one year, with hearings taking longer.

The most common reason secondary claims are denied is a weak nexus opinion. If the C&P examiner concluded that your secondary condition is “less likely than not” related to the primary disability, obtaining a detailed rebuttal opinion from a private specialist and filing a supplemental claim is often the fastest path to reversal. Focus the new opinion on the specific reasons the examiner gave for the negative finding, not just a restatement of the earlier conclusion.

1
eCFR. 38 CFR 3.310 – Disabilities That Are Proximately Due to, or Aggravated by, Service-Connected Disease or Injury
2
eCFR. 38 CFR 3.310 – Disabilities That Are Proximately Due to, or Aggravated by, Service-Connected Disease or Injury – Section (b)
3
Board of Veterans’ Appeals. BVA Decision A25014545
4
U.S. Department of Veterans Affairs. Types of Disability Claims and When To File
5
eCFR. 38 CFR 3.102 – Reasonable Doubt
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U.S. Department of Veterans Affairs. File for Disability Compensation With VA Form 21-526EZ
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U.S. Department of Veterans Affairs. How To File a VA Disability Claim
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U.S. Department of Veterans Affairs. Your Intent To File a VA Claim
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eCFR. 38 CFR 3.655 – Failure To Report for Department of Veterans Affairs Examination
10
eCFR. 38 CFR 4.25 – Combined Ratings Table
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eCFR. 38 CFR 4.14 – Avoidance of Pyramiding
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U.S. Department of Veterans Affairs. Choosing a Decision Review Option