GFR is a kidney filtration estimate
The GFR Calculator estimates glomerular filtration rate from age, sex, and serum creatinine. The local solver returns a value in mL/min/1.73m2 and labels the broad CKD stage band associated with that number.
This page is for understanding a lab-style estimate. Kidney results should be reviewed with a qualified healthcare professional.
Serum creatinine must use mg per dL
The creatinine field expects mg/dL. Some lab reports use different units, such as micromoles per liter. Entering a value in the wrong unit can make the estimate dangerously misleading.
Use the exact value and unit from the lab report, and convert only when the conversion is known.
The local method is adult only
The calculator rejects ages below 18 because the local equation is an adult eGFR estimate. Children and teens need pediatric kidney equations and clinician interpretation.
Age is not a minor field here. It directly affects the estimate.
Sex selection changes the equation branch
The local solver uses different constants for the male and female selections. That helps the equation represent broad creatinine differences, but it does not capture every individual factor affecting muscle mass or creatinine generation.
If the sex selection is clinically uncertain or the result will guide care, ask the clinician or lab which value should be used.
One eGFR value does not diagnose kidney disease alone
An eGFR result is usually interpreted with urine albumin, repeat testing, medical history, medications, hydration status, blood pressure, diabetes status, and other labs. A single calculator result cannot diagnose or rule out kidney disease.
Unexpected values should be discussed with the ordering clinician rather than self-interpreted from the stage label alone.
Creatinine can be affected by more than filtration
Creatinine comes partly from muscle metabolism. Body size, muscle mass, diet, supplements, recent intense exercise, illness, and some medications can affect the value. That is one reason eGFR is an estimate instead of a direct measurement.
Body surface area adjustment is built into the label
The eGFR output is normalized to 1.73 m2 body surface area. That convention makes results more comparable, but some dosing or specialty decisions may require different handling.
For a general BSA estimate from height and weight, the Body Surface Area Calculator is a separate page.
Lab trends matter more than isolated guesses
Kidney function is often interpreted by trend. A stable result over time can mean something different from a sudden drop. Lab timing, hydration, illness, and medication changes can all affect the pattern.
Save the test date with the value when comparing results.
Symptoms and urgent concerns are outside the calculator
Severe weakness, confusion, chest pain, shortness of breath, very low urine output, severe swelling, or other urgent symptoms need medical care. A web calculator should not delay urgent evaluation.
Use the CKD band as a discussion cue
The stage band in the output can help someone understand the general range, but it should not be treated as a full diagnosis. CKD staging also uses persistence over time and markers of kidney damage.
Keep the original lab report nearby
A useful note includes serum creatinine, unit, age, sex selection, estimated GFR, lab date, and whether the value came from a repeat test. The original report may include flags, reference notes, and other kidney markers that the calculator does not show.
Nutrition calculators are not kidney diet tools
Protein, potassium, sodium, phosphorus, and fluid advice can change when kidney disease is present. General pages such as the Protein Calculator are not kidney-diet prescriptions.
Ask before changing medication or supplements
An eGFR estimate can affect medication decisions, imaging contrast discussions, or supplement safety. Do not stop, start, or change treatment based only on a calculator output.
Bring the result to a clinician or pharmacist if it raises concern.