Neurology / Chronic illness
Fatigue Severity Scale (FSS)
The FSS is a 9-item questionnaire widely used in multiple sclerosis, chronic fatigue syndrome, post-COVID conditions, and other chronic illnesses. Patients rate agreement with statements about fatigue’s effects on daily life.
1. My motivation is lower when I am fatigued
2. Exercise brings on my fatigue
3. I am easily fatigued
4. Fatigue interferes with my physical functioning
5. Fatigue causes frequent problems for me
6. My fatigue prevents sustained physical functioning
7. Fatigue interferes with carrying out certain duties and responsibilities
8. Fatigue is among my three most disabling symptoms
9. Fatigue interferes with my work, family, or social life
Fatigue impact currently mild. Continue monitoring and supportive strategies.
How to Use This Calculator
Have the patient rate each item
Ensure the patient understands the 1–7 scale and focuses on the past week’s fatigue impact.
Review total and average scores
Total score ranges 9–63; average 1–7. Values ≥ 4 often indicate clinically significant fatigue.
Integrate into treatment planning
Use scores to track trends, evaluate interventions, and communicate fatigue burden with multidisciplinary teams.
Formula
Total FSS score = Sum of item scores (range 9–63)
Average FSS = Total ÷ 9 (range 1–7)
Averages ≥ 4 are typically considered clinically significant fatigue.
Full Description
The Fatigue Severity Scale was developed for patients with multiple sclerosis and systemic lupus erythematosus but is widely used across chronic conditions. It correlates with functional impairment, depression, and quality of life. Clinicians use the FSS to monitor fatigue and evaluate therapy responses.
Combine FSS results with medical evaluation to identify reversible causes (anemia, thyroid disease, medication effects) and to plan multidisciplinary management (sleep hygiene, graded exercise therapy, cognitive behavioral therapy).
Frequently Asked Questions
How often should the FSS be repeated?
Every 4–8 weeks during active treatment, or at routine follow-up visits, to monitor trends.
Is the FSS validated for post-COVID fatigue?
Yes, studies have applied FSS to long COVID cohorts, although disease-specific tools are also emerging.
What if the patient has cognitive impairment?
Provide assistance or caregiver input. Document any concerns about response reliability.
Can FSS guide return-to-work decisions?
Use the FSS in conjunction with functional assessments and occupational therapy evaluations to support individualized plans.