What is eGFR?
The estimated Glomerular Filtration Rate (eGFR) measures how well your kidneys filter waste from your blood each minute. It is the best overall indicator of kidney function and is used worldwide to detect, monitor, and manage chronic kidney disease (CKD).
CKD Stages by eGFR
| Stage | eGFR (mL/min/1.73m²) | Description |
|---|---|---|
| G1 | ≥ 90 | Normal or high function |
| G2 | 60 – 89 | Mildly decreased |
| G3a | 45 – 59 | Mild to moderate decrease |
| G3b | 30 – 44 | Moderate to severe decrease |
| G4 | 15 – 29 | Severely decreased |
| G5 | < 15 | Kidney failure (dialysis / transplant) |
About the Formulas
CKD-EPI 2021 — The current gold standard recommended by KDIGO and the National Kidney Foundation. Updated in 2021 to remove the race coefficient, making it fairer and more universally applicable.
MDRD (4-variable) — Modification of Diet in Renal Disease. Widely used for over 20 years, tends to underestimate eGFR in healthy individuals but performs well in established CKD.
Cockcroft-Gault — Estimates creatinine clearance (CrCl) using body weight. Still used for drug dosing calculations. Less accurate for GFR classification.
Which Formula Should I Use?
If you are unsure, CKD-EPI 2021 is the best default choice for most people. Here is a simple guide to help you decide:
| Formula | Best Used When… |
|---|---|
| CKD-EPI 2021 | General kidney function screening, routine check-ups, monitoring CKD, or when no specific reason exists to use another formula. Recommended by the National Kidney Foundation and KDIGO for all adults. |
| MDRD | When your doctor specifically requests it, or when comparing to older test results calculated with MDRD. Also used in some hospital lab systems. Note: tends to underestimate eGFR when kidney function is normal or near-normal. |
| Cockcroft-Gault | When a doctor or pharmacist needs to adjust medication dosing based on kidney function. Requires your body weight and estimates creatinine clearance (CrCl), not true GFR. Not used for CKD staging. |
| All Three | Useful for comparison or when you want to see the range of estimates. If results differ significantly between formulas, discuss this with your doctor. |
💡 In clinical practice, most hospitals and labs now report eGFR using CKD-EPI 2021 automatically alongside your creatinine result.
How to Obtain Your Serum Creatinine
Serum creatinine is measured from a simple blood test ordered by a doctor. You cannot measure it at home — it requires a laboratory analysis. Here is how to get your result:
- See your GP or doctor — ask for a kidney function test, also called a renal panel, U&E (urea & electrolytes), or basic metabolic panel (BMP). Creatinine is always included.
- Check existing blood test results — if you have had recent blood work, look for "creatinine" or "Cr" on the results. It is typically reported in mg/dL (US) or µmol/L (Australia, UK, Europe).
- Unit conversion — this calculator uses mg/dL. If your result is in µmol/L, divide by 88.4 to convert. For example, 88 µmol/L ÷ 88.4 = 1.0 mg/dL.
- Fasting is not required — unlike cholesterol or glucose tests, creatinine can be measured at any time of day. However, avoid a very large meat meal in the 12 hours beforehand, as this can temporarily raise levels.
- Online health portals — many hospitals and GP clinics provide a patient portal (e.g. MyHealth Record in Australia, MyChart in the US) where you can view past blood test results directly.
- Normal reference range — approximately 0.6–1.2 mg/dL for men and 0.5–1.1 mg/dL for women, though ranges vary slightly between laboratories.
💡 A single creatinine reading has limited meaning alone — eGFR calculated from it, tracked over time, gives a much clearer picture of kidney health.
What Affects Creatinine?
- Muscle mass — higher muscle = higher creatinine (not always poor kidney function)
- Diet — a large meat meal can temporarily raise creatinine
- Hydration — dehydration falsely elevates creatinine
- Medications — some drugs (e.g. trimethoprim, cimetidine) block tubular secretion
- Age — creatinine production declines with age and muscle loss
When to See a Doctor
- eGFR below 60 on two separate tests ≥ 3 months apart indicates CKD
- Rapid decline of >5 mL/min/1.73m² per year warrants urgent review
- eGFR below 30 — refer to nephrologist
- eGFR below 15 — urgent kidney replacement therapy planning