Fatigue Severity Scale (FSS)
Last reviewed
FSS: Self-Report Fatigue Questionnaire
The Fatigue Severity Scale (FSS) is a 9-item questionnaire that measures the impact of fatigue on daily functioning. It was developed by Krupp and colleagues in 1989 and has become one of the most widely used fatigue instruments in clinical research and practice. Each item is a statement about fatigue, and you rate your agreement on a scale from 1 (strongly disagree) to 7 (strongly agree). Your score is the mean of all nine items.
The FSS does not measure how tired you feel in the moment. Instead, it captures how much fatigue interferes with your life over the preceding week: your motivation, exercise capacity, ability to carry out duties, and physical functioning. This makes it particularly useful for people with post-viral conditions, ME/CFS, and other chronic illnesses where fatigue is persistent and functionally limiting rather than simply a feeling of tiredness.
The FSS was developed in multiple sclerosis and lupus, and a larger validation in 2008 added stroke and sleep disorders. If your fatigue worsens disproportionately after activity, the post-exertional malaise questionnaire characterises that pattern specifically; for a broader quality-of-life profile, see the RAND-36. Another fatigue measure often used in the UK is the Chalder Fatigue Scale, which scores the symptom itself rather than its impact; the two complement each other.
This is a free, interactive version. Complete it below and receive your score immediately. No sign-up or email is required.
Your FSS score
Item breakdown
| Statement | Your rating |
|---|---|
| Mean score |
Your results over time
Complete this again in a few weeks and the change will show here.
Symptom scores change slowly. A monthly retake is enough to see a trend.
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Understanding your FSS score
What the score measures
It measures how much fatigue affects your daily life: your motivation, exercise, physical functioning, duties, and work, family or social life. You rate nine statements about the past week from 1 (strongly disagree) to 7 (strongly agree), and your score is the average of the nine, from 1 to 7. Higher means fatigue has more impact.
It was developed in multiple sclerosis and lupus (Krupp et al. 1989) and later checked in more than 1,300 people in Switzerland (Valko et al. 2008).
FSS score interpretation
In the largest validation study, 454 healthy adults in Switzerland averaged 3.0, and the authors suggested reading a score of 4 or more as a sign of fatigue. Even so, 18% of that healthy group scored 4 or more. In the original 1989 study, 20 healthy adults averaged 2.3.
| Group | Average | Scoring 4 or more |
|---|---|---|
| Healthy adults, original study (n = 20) | 2.3 | not reported |
| Healthy adults (n = 454) | 3.0 | 18% |
| After ischaemic stroke (n = 235) | 3.9 | 49% |
| Sleep-wake disorders (n = 429) | 4.3 | 62% |
| Multiple sclerosis (n = 188) | 4.7 | 69% |
A score of 5 or more is above the cut-off of 4 and above the average of every patient group in the Swiss validation study, which ranged from 3.9 after stroke to 4.7 in multiple sclerosis. Only 3.5% of the healthy adults scored above 5.2, the healthy average plus two standard deviations. It means fatigue is having a large effect on your life, but it does not say why.
Your result is shown to one decimal place and judged on that number, so 4.0 counts as 4 or more.
What a change in score means
No minimal important change has been published for post-viral illness or ME/CFS. In a survey of 365 people with multiple sclerosis, differences of 0.45 to 0.88 points went with a meaningful difference in quality of life, and the authors suggest at least 0.45. That compared different people at one point in time rather than one person over time, so treat it as a rough guide.
The questions cover the past week, so one bad week can move your score; a monthly trend says more than any single pair. The multiple sclerosis figures come from Rooney et al. 2019.
What it does not measure
No. It measures how much fatigue gets in the way, not what causes it, and it does not ask about post-exertional malaise, sleep or thinking problems. High scores are common in many conditions, including multiple sclerosis, stroke and sleep disorders.
For worsening after effort, see the DSQ-PEM and the post-exertional malaise explainer. The Chalder Fatigue Scale scores the fatigue itself.
Taking this to your GP or consultant
Bring the score, the date, the trend from your saved results, and a note of which statements you rated 6 or 7. Describe it as a nine-question measure of how much fatigue interferes with daily life, developed in multiple sclerosis and now one of the most commonly used fatigue questionnaires. It can show that fatigue is substantial and how it has changed. It cannot show the cause, and it is not a test for ME/CFS or long COVID. See preparing for a GP appointment.
Sources and licence
Based on: Krupp LB, LaRocca NG, Muir-Nash J, Steinberg AD. The fatigue severity scale. Application to patients with multiple sclerosis and systemic lupus erythematosus. Arch Neurol. 1989;46(10):1121–1123.
- Krupp LB, LaRocca NG, Muir-Nash J, Steinberg AD. The fatigue severity scale: application to patients with multiple sclerosis and systemic lupus erythematosus. Arch Neurol 1989;46(10):1121–1123. Article
- Valko PO, Bassetti CL, Bloch KE, Held U, Baumann CR. Validation of the fatigue severity scale in a Swiss cohort. Sleep 2008;31(11):1601–1607. Full text
- Rooney S, McFadyen DA, Wood DL, Moffat DF, Paul PL. Minimally important difference of the fatigue severity scale and modified fatigue impact scale in people with multiple sclerosis. Mult Scler Relat Disord 2019. Article