Measure self-reported fatigue burden with the 9-item Fatigue Severity Scale and its mean 1-to-7 score.
The Fatigue Severity Scale (FSS) is a 9-item self-report questionnaire that measures how strongly fatigue affects day-to-day life. Each item is rated from 1 to 7, and the mean item score is the main output.
The FSS was originally developed and validated in adults with multiple sclerosis and systemic lupus erythematosus, and it is now used more broadly as a practical self-report fatigue measure. The key number on the page is the mean score, with 4 or higher commonly used as a threshold for clinically significant fatigue.
This page is designed as a screening and tracking aid. It does not identify the cause of fatigue and it should not be treated as a disease-specific treatment algorithm.
Fatigue is common, but it is hard to compare over time without a structured measure. The FSS helps turn a vague complaint into a repeatable score that can be tracked across visits or interventions.
It is most useful for documenting the burden of fatigue and whether it is changing, not for telling you why the fatigue is happening.
FSS Mean = (Sum of all 9 item scores) / 9 Range: 1.0-7.0 Higher values indicate greater self-reported fatigue burden Mean score >= 4 is a commonly used threshold for clinically significant fatigue
Result: FSS Mean 4.5 — Clinically Significant Fatigue
A mean FSS score of 4.5 is above the commonly used threshold of 4.0, suggesting meaningful self-reported fatigue burden. The next step is to interpret that result in the context of the underlying condition and possible contributors.
The FSS is good at summarizing how burdensome fatigue feels and whether it is interfering with ordinary life. That makes it useful in follow-up, research, and structured symptom review.
It is not a cause finder, not a sleep study, and not a disease-specific management algorithm. A high score can occur in many medical and non-medical situations.
Use the FSS as a repeatable symptom measure. Its value comes from documenting burden and change over time, not from pretending the number alone explains the fatigue.
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This page applies the original Fatigue Severity Scale by averaging the nine 1-to-7 item scores into the standard mean score. The mean score is the main output because that is the conventional FSS summary used in the original validation work and later fatigue-screening studies.
The page is intended as a self-reported fatigue-burden measure rather than a cause-finding tool. A mean score of 4 or higher is a common threshold for clinically significant fatigue, but the number still has to be interpreted alongside sleep, mood, medications, chronic illness, and the broader clinical context.
It measures self-reported fatigue burden and how strongly fatigue interferes with daily life. It does not identify the cause of fatigue.
No. A high FSS can occur in many settings and is not specific to one diagnosis.
Fatigue is a sense of exhaustion or reduced energy, while sleepiness is a tendency to fall asleep. The two can overlap, but they are not the same thing.
A mean score of 4 or higher is a commonly used threshold for clinically significant fatigue, but the interpretation still depends on the clinical setting.
Yes. That is one of its main practical uses. Repeating the scale can help show whether the fatigue burden is changing.
The standard FSS was developed for adults. Pediatric fatigue assessment usually uses other tools.