Loading...
Printed on 7/20/2026
For informational purposes only. This is not medical advice.
The Frailty Index (FI) based on 40 deficits quantifies frailty as the proportion of accumulated health deficits. It follows the deficit-accumulation model, where FI = deficits present divided by total deficits considered. Higher values reflect greater biologic vulnerability and are associated with higher risks of hospitalization, disability, institutionalization, and mortality.
Formula: FI-40 = deficits present / 40 (range 0-1).
Save your results with a free account
Keep a history of calculations, favorite tools, and access your dashboard anytime.
The FI-40 surveys 40 predefined health deficits spanning multiple domains: symptoms (fatigue, dizziness), signs (peripheral edema, skin problems), diseases (diabetes, hypertension, heart failure), disabilities (ADL and IADL difficulties), and laboratory abnormalities. Each deficit is scored as absent (0) or present (1). Validity requires deficits that occur in roughly 1 to 70 percent of the population. Clinical data from medical history, physical examination, and standard investigations are used to complete the assessment systematically.
FI = deficits present / 40. The result is a continuous value between 0 and 1. In practice, the FI rarely exceeds 0.67 — a natural upper limit observed consistently across populations, thought to represent the maximum deficit burden compatible with survival. FI above 0.25 generally indicates frailty. The continuous nature captures gradations of risk that categorical tools miss, making it useful for serial monitoring and quantitative risk communication.
Working risk bands: FI below 0.10 (fit), FI 0.10 to 0.19 (mildly vulnerable), FI 0.20 to 0.24 (pre-frail), FI 0.25 or higher (frail), FI 0.40 or higher (severely frail). FI above 0.25 corresponds roughly to the Fried Frailty Phenotype. Serial measurement tracks health trajectory: a rising FI reflects worsening vulnerability, while a stable or falling FI can validate intervention effectiveness. Identifying specific remediable deficit clusters guides targeted intervention.
Surgeons, anesthesiologists, perioperative medicine teams
The FI-40 provides granular frailty quantification beyond single-domain tools in perioperative risk. Patients with FI above 0.25 have significantly higher rates of postoperative complications, prolonged stay, and 30-day mortality. The continuous score quantifies incremental risk. Identifying specific deficit clusters (polypharmacy, cardiac comorbidities, functional limitation) enables targeted prehabilitation. Pair with [Clinical Frailty Scale](/tools/clinical-frailty) for rapid global frailty staging.
Geriatricians, internists, primary care physicians
The FI-40 excels for serial measurement, detecting accelerating deficit accumulation before it manifests as acute crisis. In heart failure, COPD, and CKD, rising FI values predict adverse events weeks to months before clinical deterioration. A change of 0.03 or more over 6 to 12 months is clinically meaningful, warranting care plan review, medication rationalization, and rehabilitation referral. A falling FI after optimizing remediable conditions validates treatment benefit.
Researchers, epidemiologists, health system analysts
The FI remains the gold standard for quantifying frailty in longitudinal studies and clinical trials. Its continuous scale enables parametric statistical analysis and detection of small intervention effects. FI can be constructed retrospectively from EHR data — enabling large-scale studies without prospective collection. The electronic Frailty Index (eFI) from EHR data has become a practical population-level tool for primary care panel screening.
Cardiologists, cardiac surgeons, cardiac rehabilitation teams
FI substantially improves risk prediction in TAVI, cardiac surgery, and electrophysiology beyond STS and EuroSCORE, identifying patients at prohibitive surgical risk better suited for transcatheter or conservative approaches. In heart failure, FI predicts 30-day readmission, cardiac rehabilitation response, and end-of-life trajectory independent of ejection fraction. Patients with FI above 0.40 and advanced heart failure benefit from early palliative care integration.
Oncologists, geriatric oncology teams, palliative care physicians
The FI-40 provides more granular frailty data than performance status scores in older adults with cancer. Patients with FI above 0.30 have significantly higher rates of chemotherapy toxicity and treatment discontinuation. FI is used alongside the [G8 screening tool](/tools/geriatric-8-g8): G8 identifies who needs comprehensive geriatric assessment, FI-40 quantifies frailty burden. Very high FI above 0.45 supports shifting goals toward quality of life over disease-modifying therapy.
Palliative care teams, geriatricians, hospitalists
The FI-40 provides objective quantitative data for difficult conversations about prognosis and treatment intensity. FI 0.45 means 18 of 40 health deficits are present — a tangible framing for patients and families. FI above 0.35 to 0.40 is associated with clinically significant 1-year mortality, supporting proactive advance care planning especially in multimorbid patients without a single dominant diagnosis.
The FI rarely exceeds 0.67 across all studied populations — this consistent upper limit is thought to reflect a threshold of deficit burden incompatible with survival. Clinically, a calculated FI above 0.60 indicates an individual in the most extreme health decrement range and almost always warrants urgent palliative and supportive care review. Values above 0.70 should prompt data quality review before clinical use.
Annual FI accumulation in community-dwelling older adults averages about 0.03/year. For serial monitoring, a change of 0.03 or more between assessments is a meaningful signal. Faster accumulation suggests accelerated aging or unaddressed health problems. Track trajectory — consistently rising or falling FI over two or more assessments — rather than relying on any single cross-sectional value.
While developed in elderly populations, the FI has validated predictive value in middle-aged adults and younger adults with chronic disease, reflecting the universal biology of deficit accumulation as a marker of biological rather than chronological aging. FI 0.30 in a 50-year-old has similar adverse-outcome implications as in a 75-year-old.
The FI captures health deficit breadth but does not directly measure physical performance. Pair with [4-meter walking speed](/tools/walking-speed-4m) and [5x sit-to-stand](/tools/five-times-sit-to-stand) to add objective physical function data. FI 0.28 with gait speed below 0.8 m/s identifies a patient with both high biological vulnerability and measurable physical impairment — a high-risk combination warranting urgent multidisciplinary intervention.
When reviewing a high FI, categorize deficits as remediable vs. non-remediable. Common remediable deficits include undertreated depression, pain, anemia, vitamin D deficiency, dehydration, polypharmacy adverse effects, and sensory impairment. Systematically addressing these can reduce FI by 0.05 to 0.15 over 3 to 6 months, with direct functional and survival implications.
The FI is a population-level risk tool. Individual patients with high FI values can have good outcomes when deficits are remediable and social support and resilience are strong. Use FI to structure risk discussions and identify intervention targets — not to make automatic treatment decisions. Always integrate patient values and preferences.
The eFI derived from routine primary care EHR data allows frailty screening across entire patient panels. eFI 0.12 or higher corresponds to mild frailty and identifies patients benefiting from proactive care review. Practices using eFI screening have demonstrated earlier high-risk patient identification, improved advance care planning rates, and reduced emergency hospitalizations.
FI approximately 0.25 is generally concordant with Fried Frailty Phenotype diagnosis (3 or more of 5 criteria). This alignment enables cross-tool communication — a patient with FI 0.28 likely meets Fried frailty criteria. Use the FI as a screening tool identifying who should undergo phenotype assessment.
Frailty Index interpretation is continuous; category bands are practical risk-communication groupings rather than universally fixed diagnostic thresholds.
Higher FI-40 values indicate higher cumulative frailty burden and support more proactive risk-informed care planning.
Use in geriatric assessment, longitudinal monitoring, and research or quality pathways where a deficit-accumulation frailty model is desired.
Results depend on deficit selection and data completeness; FI should be interpreted alongside functional and clinical context, not in isolation.
For related assessments, see Electronic Frailty Index, Clinical Frailty Scale and FRAIL Scale.
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.
April 21, 2026 · trust-baseline
Clinical trust metadata enabled for this tool page with structured review/version fields.
Classify eFI values into fit, mild, moderate, or severe frailty categories using common thresholds.
OpenGeriatricsAssess frailty using the Rockwood Clinical Frailty Scale (CFS 1–9): Very Fit to Terminally Ill. Used for hospice eligibility, prognostication, ICU triage, surgical risk stratification, and goals-of-care discussions.
OpenGeriatricsScreen frailty using the 5-item FRAIL scale (Fatigue, Resistance, Ambulation, Illnesses, Loss of weight).
OpenGeriatricsClassify hospital frailty risk category from HFRS value (<5 low, 5-15 intermediate, >15 high).
Open