By Naomi Foster, Health Writer, Encore Editorial. Last updated .
Every number on MedCalcTools comes out of a public equation, not a judgment call about your health. This page explains what that distinction means in practice: what a calculator can tell you, what it cannot, and why a result here sometimes reads differently than the same measurement on a lab report or a chart.
Education, not diagnosis
A calculator on this site takes the numbers you type in and runs them through one named formula. It has no history, no exam, and no lab values beyond what you entered. That is enough to reproduce a known equation, and nowhere near enough to diagnose, rule out, or manage a condition. Treat every result as a worked example of the math, not a finding about your body.
Why the number here can differ from your lab report
Labs and calculators often answer slightly different questions even when they start from the same formula. A creatinine clearance printed on a lab report may already be adjusted to a lab's own convention, while the Cockcroft-Gault tool on this site reports the raw clearance in milliliters per minute exactly as published in 1976. The two kidney-function numbers on this site, Cockcroft-Gault clearance and the 2021 CKD-EPI eGFR, are not interchangeable either. They were built for different jobs: drug-dosing tables were largely validated against Cockcroft-Gault, while CKD staging today uses CKD-EPI. Sodium correction makes the point even more clearly. The Katz and Hillier calculators here use two different published coefficients, 0.016 and 0.024, for the same glucose input, because the literature has never settled on one correction factor for every glucose level. Corrected calcium works the same way: it adds a fixed offset to your measured calcium based on albumin using the Payne formula, but a hospital lab may use a locally validated version that differs slightly. None of that means one number is wrong and the other right. It means each formula is a specific tool built to answer a specific question, and two reasonable tools can land on two reasonable answers.
Reading a result without over-reading it
A calculator result is most useful next to context you already have: a trend over time, a category boundary, or a target a provider already gave you. It is least useful treated as a verdict on its own. If a number surprises you, sits close to a clinical cutoff, such as the CDC line between healthy weight and overweight on the BMI tool, or would change a medication dose, that is exactly the situation where a formula's limits matter most and a clinician's judgment should carry more weight than the arithmetic.
When to bring a result to a clinician
Bring a number from this site to a doctor, nurse, or pharmacist rather than acting on it alone whenever it is unexpected, borderline, tied to a dose, or part of managing an ongoing condition such as kidney disease or diabetes. A clinician can weigh the result against your history, your other lab values, and your symptoms, which is exactly what a reference page like this one is not built to do.
What we do not claim
We do not claim this content has been reviewed by a physician, and we do not present any calculator as a diagnostic tool. Each page names its source equation and carries a visible last-updated date so you can judge its currency for yourself. If a formula on this site looks outdated or coded incorrectly, tell us through contact and we will fix it.