The disability benefits system was largely designed around visible, stable, measurable impairment. A wheelchair. A limb. A clear diagnosis on a standard list.
People with ME/CFS, POTS, fibromyalgia, MCAS, and similar conditions are rarely visible. Their impairment fluctuates. Their diagnoses are contested or recent or missing entirely. They may have good days. They may not look sick.
This is not a fringe problem. It affects millions of people, and the consequences — financial catastrophe, worsening health, loss of housing — are severe.
The fundamental problem with assessments
Most disability benefit assessments — whether PIP in the UK, SSI/SSDI in the US, or equivalent systems elsewhere — were designed to assess functional capacity based on a single observation, or based on a written account of what the applicant can do.
Neither of these works for variable-capacity conditions. If you have a relatively better day on the day of your assessment, you may appear more functional than you are. If the assessment asks what you "can" do, the honest answer is that it depends — on the day, on the preceding days, on whether you've been pushed into a flare by the stress of the appointment itself.
What assessors are not telling you
- →You are being assessed on your worst representative day, not your best day or your average day
- →Post-exertional malaise (PEM) is a legitimate functional impairment — document it explicitly
- →The cost of an activity matters, not just the ability to perform it — if you can shower but spend the rest of the day in bed recovering, that is a relevant functional limitation
- →Cognitive symptoms (brain fog, memory, concentration) are assessable functional impairments
- →You are not required to demonstrate improvement — you are required to demonstrate current impairment
Building a documentation record that supports your claim
The most effective thing you can do before applying is build a longitudinal record. A symptom diary kept for three to six months — logging your energy levels, activities, crash days, and how activities affect you — is substantially more useful than a verbal account in an assessment.
The record should capture: what you did, what it cost you (in energy and recovery time), how it affected the following 24-48 hours. This directly addresses the PEM problem: it shows, on paper, that activities have delayed consequences that aren't visible in a single assessment.
Medical evidence and the GP problem
Medical evidence is central to most disability benefit applications. For people with conditions that many GPs are not familiar with, or that don't appear on standard diagnostic lists, this is a significant obstacle.
Specialist letters carry more weight than GP letters. If you have a specialist diagnosis (cardiologist for POTS, specialist for ME/CFS), get a letter from them specifically. If you don't have specialist involvement, a GP letter that describes your symptoms, functional limitations, and trajectory is still better than nothing.
Be specific in what you ask your GP to include: not just the diagnosis, but the functional impact. Not "patient has POTS" but "patient is unable to stand for more than [X] minutes without experiencing [specific symptoms], which affects their ability to [specific activities]."
Appeals — the most important thing most people don't know
Initial rejection rates for many disability benefits are very high. Appeal rates are also very high. If you are rejected, appeal. With good documentation, advocacy, and ideally representation, appeals succeed at rates that make the initial application look like a formality.
Many people do not appeal because rejection feels like confirmation that they were wrong about their own condition. It isn't. Initial assessments are often wrong, and the appeals process exists precisely because they are wrong.
“An initial rejection is not a verdict. It is a round one.”
The Patient Advocate track at Spooniversity covers benefits navigation, documentation strategy, and system advocacy as part of a 4-month curriculum. Designed for people who are tired of navigating systems that weren't built for them — and want to learn to do it better, and help others do the same.