The Bell Disability Scale for ME/CFS: What Each Level Means
If you live with ME/CFS, you've probably seen people describe themselves as "a 30" or "around 20 on a bad week". They're usually talking about the Bell CFS Disability Scale, the most widely used way of putting a number on how much ME/CFS limits daily life. Here's what it is, what each level means and how to use it.
Where it comes from
The scale was published by Dr David Bell, a US physician who worked with ME/CFS patients for decades, in his 1995 book The Doctor's Guide to Chronic Fatigue Syndrome. It runs from 0 to 100 in steps of 10. Unlike many illness scales, higher is better: 100 is full health and 0 is completely bedbound. You pick the description that fits your typical day most closely.
The levels
| Score | What it looks like |
|---|---|
| 100 | No symptoms at rest or with activity. Normal activity, able to work full time. |
| 90 | No symptoms at rest, mild symptoms with activity. Normal activity, able to work full time. |
| 80 | Mild symptoms at rest, worse with exertion. Only exertion-heavy activities are limited. |
| 70 | Mild symptoms at rest. Some daily limitation; functioning at about 90 percent of what you would expect. |
| 60 | Mild to moderate symptoms at rest. Daily limitation, functioning at about 70 to 90 percent; can't work full time in physical jobs. |
| 50 | Moderate symptoms at rest, moderate to severe with activity. Overall activity about 70 percent of expected. |
| 40 | Moderate symptoms at rest, moderate to severe with activity. Overall activity about 50 to 70 percent of expected. |
| 30 | Moderate to severe symptoms at rest, severe with any exertion. Overall activity about 50 percent of expected. |
| 20 | Moderate to severe symptoms at rest. Unable to do strenuous activity; overall activity 30 to 50 percent of expected. |
| 10 | Severe symptoms at rest. Bedridden most of the time, no travel outside the house. |
| 0 | Severe symptoms continuously. Bedridden constantly, unable to care for yourself. |
Roughly speaking, scores of 70 and above are often described as mild ME/CFS, 40 to 60 as moderate, 20 to 30 as severe and 10 or below as very severe, although clinicians draw those lines a little differently.
Why it's useful
- It describes function, not just symptoms. ME/CFS is about what you can do without paying for it later. The scale captures that in a way a symptom checklist doesn't.
- It's shared language. Patients, researchers and many clinicians use it, so "I've gone from 50 to 30 this year" is understood quickly.
- It shows change over months. Slow decline or gradual improvement is hard to notice day to day. A score recorded regularly makes it visible.
Using it well
Rate your typical level, not your best day. Many people with ME/CFS can push to a higher level for a day and then crash, so a score taken on a good day can overstate what's sustainable. It also helps to keep two numbers apart: your usual baseline, and how you are today. During a crash, today's number can drop well below your baseline and then recover, and seeing both side by side shows whether a bad stretch is a temporary crash or a real change in your baseline.
If you're applying for disability benefits or explaining your situation to a doctor or employer, a record of your Bell score over several months, alongside what you did each day, is far more convincing than a single number.
Track your baseline and your day with Mya
Mya asks for your usual Bell level when you start, records how you are each day, and links crashes back to the exertion that likely caused them, so changes in your baseline show up over time.
This article is for general information and isn't a substitute for medical advice. Talk to a doctor about your own symptoms, tests and treatment.