Polypharmacy Risk Score Calculator
Drug interaction risk from medication count, high-risk classes, renal function, and anticholinergic burden.
About this calculator
Polypharmacy -- commonly defined as taking five or more regular medications, with ten or more sometimes called hyperpolypharmacy -- is a well-established marker of increased drug interaction and adverse event risk in older adults (Masnoon et al. 2017; Gnjidic et al. 2012), and this calculator's polypharmacy-level classification uses those published cutoffs directly.
The interaction-risk score underneath it, though, is this calculator's own illustrative model rather than a validated clinical instrument: it starts from the number of possible medication PAIRS a patient's total medication count creates (five medications create ten pairs, ten medications create forty-five), assumes roughly a 2% chance any given pair interacts, and combines that base probability with multipliers for high-risk drug classes (anticoagulants, opioids, insulin, digoxin, lithium, and similar), for age past 75 and especially past 85, for reduced renal clearance (eGFR below 60, with the multiplier growing sharply below 30 and below 15), and for accumulated anticholinergic burden. Those specific multiplier values are illustrative weights this calculator chose to combine several real, separately-documented risk factors into one composite number, not themselves drawn from a single validated scoring instrument, so treat the resulting percentage as a rough orientation rather than a clinically calibrated probability. Fall risk and deprescribing- opportunity scores are separate composites built from an overlapping but not identical set of the same inputs, meant to flag where a medication review would have the most to offer.
Medical Disclaimer
This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.
Inputs
Results
Interaction risk score
27.4
How to Use This Calculator
- Enter Total medications (all scheduled and PRN drugs) and how many of those are High-risk medications (anticoagulants, opioids, insulin, digoxin, lithium, and similar).
- Enter Patient age and eGFR from the most recent renal function labs.
- Enter the Anticholinergic burden score (0-10) and the number of PRN medications.
- Review the Interaction risk score, Polypharmacy level, and Estimated potential interactions.
- Check the ADE risk category, Fall risk from medications, and Deprescribing opportunity score to prioritize a medication review.
How the result changes with Total medications
| Total medications | Interaction risk score |
|---|---|
| 2.5 | 8.8 |
| 3.75 | 17.1 |
| 7.5 | 64.8 |
| 13 | 100 |
What each input means
- Total medications
- Total number of scheduled and PRN medications the patient takes.
- High-risk medications
- Number of high-risk drugs (anticoagulants, opioids, insulin, digoxin, lithium, etc.). Clamped to Total medications -- can't exceed the total drug count.
- Patient age
- Patient age in years. Risk increases sharply after age 75 and 85.
- eGFR
- Estimated glomerular filtration rate. Lower eGFR means reduced drug clearance.
- Anticholinergic burden score
- Sum of anticholinergic burden from all medications (0-10 scale).
- PRN medications
- Number of as-needed (PRN) medications — candidates for deprescribing review. Clamped to Total medications -- can't exceed the total drug count.
What each result means
- Interaction risk score
- Combined drug interaction risk (0-100). Higher = greater probability of adverse interactions.
- Polypharmacy level
- 1 = No polypharmacy (<5 meds), 2 = Polypharmacy (5-9), 3 = Hyperpolypharmacy (10+).
- Estimated potential interactions
- Approximate number of potential drug-drug interactions from this calculator's illustrative model -- not a validated count of clinically significant interactions; confirm with a pharmacologic interaction checker.
- ADE risk category (1-5)
- Adverse drug event risk: 1 = very low, 5 = very high.
- Fall risk from medications
- Medication-related fall risk score (0-100).
- Deprescribing opportunity
- Score indicating potential benefit from medication review and deprescribing (0-100).
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersTotal medications = 5, High-risk medications = 1, Patient age = 75, eGFR = 60 = 6 input(s) provided
- Calculate Interaction risk scoreInteraction risk score27.4 = 27.4
- Calculate Polypharmacy level2 = 2
- Calculate Estimated potential interactionsEstimated potential interactions0.3 = 0.3
Engine last updated . Checked against 3 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
What medication count counts as polypharmacy versus hyperpolypharmacy?
This calculator uses the commonly cited literature cutoffs: fewer than 5 medications is not classified as polypharmacy, 5 to 9 medications is polypharmacy, and 10 or more is hyperpolypharmacy. That classification comes from the total medication count alone and does not depend on how many of those medications are considered high-risk.
Why does reduced kidney function raise the interaction risk score?
Many drugs are cleared by the kidneys, so reduced renal filtration (a lower eGFR) means drugs accumulate to higher levels and stay in the body longer than expected, raising the chance that two or more drugs interact before either is fully cleared. This calculator applies a renal-impairment multiplier that grows as eGFR drops below 60, with the largest increase below 15.
Is the interaction risk percentage this calculator shows a validated clinical score?
No -- only the polypharmacy-level classification (5+ medications, 10+ for hyperpolypharmacy) comes from published literature cutoffs. The interaction-risk percentage is this calculator's own illustrative combination of medication count, high-risk drug classes, age, renal function, and anticholinergic burden into one number, useful as a rough orientation but not a substitute for a validated pharmacologic interaction check or a pharmacist medication review.
Does anticholinergic burden affect the fall risk score the same way high-risk medications do?
Both contribute to this calculator's fall-risk score, but at different weights -- each high-risk medication adds more to the fall-risk contribution than each point of anticholinergic burden score does. Anticholinergic burden also separately affects the deprescribing-opportunity score, reflecting that anticholinergic medications are common deprescribing targets in older adults independent of their fall-risk contribution.
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