eGFR 20: What It Means (CKD Stage G4)
An eGFR of 20 mL/min/1.73m² is KDIGO category G4 (15 to 29). This page explains what it means, the creatinine behind it, and what to ask next.
Medically reviewed by Dr. Rishi Kumar Kafle, MBBS, MD, FASN. Last reviewed October 2026.
An eGFR of 20 mL/min/1.73m² falls in KDIGO category G4 (15 to 29), which means severely decreased filtration. At age 50 it matches a creatinine of about 3.56 mg/dL in a man and 2.79 mg/dL in a woman. This is below 30, the level at which KDIGO advises sharing care with a kidney specialist (nephrologist).
Where 20 Sits Within G4
An eGFR of 20 is 5 points above the G4 floor of 15. It is 10 points below the G3b line at 30. The KDIGO categories run from G1 to G5; G4 is explained in more depth on the CKD stage 4 page.
G4 is severely decreased filtration. KDIGO advises sharing care with a kidney specialist (nephrologist) once eGFR is below 30, and this is usually when planning for future treatment options begins, well ahead of any need.
What Creatinine Gives an eGFR of 20?
The creatinine behind an eGFR of 20 comes from solving the race-free CKD-EPI 2021 equation backwards, by age and sex:
| Age | Man | Woman |
|---|---|---|
| 30 | 3.95 mg/dL (349 µmol/L) | 3.10 mg/dL (274 µmol/L) |
| 40 | 3.75 mg/dL (331 µmol/L) | 2.94 mg/dL (260 µmol/L) |
| 50 | 3.56 mg/dL (314 µmol/L) | 2.79 mg/dL (247 µmol/L) |
| 60 | 3.38 mg/dL (299 µmol/L) | 2.65 mg/dL (235 µmol/L) |
| 70 | 3.21 mg/dL (283 µmol/L) | 2.52 mg/dL (223 µmol/L) |
| 85 | 2.97 mg/dL (262 µmol/L) | 2.33 mg/dL (206 µmol/L) |
A 30-year-old man reaches 20 at 3.95 mg/dL, while an 85-year-old woman reaches it at 2.33 mg/dL. The older the person, the lower the creatinine behind the same eGFR. Nearby creatinine guides: creatinine 2.5 mg/dL (221 µmol/L), creatinine 3.0 mg/dL (265 µmol/L).
eGFR 20 in Absolute mL/min
eGFR is indexed to a body surface area (BSA) of 1.73m². To compare it with a creatinine clearance, or for a very small or large adult, it can be de-indexed with eGFR × BSA ÷ 1.73. For an eGFR of 20, the absolute values are:
| Example adult | BSA (m²) | Absolute GFR (mL/min) |
|---|---|---|
| Man, 40, 178 cm, 80 kg | 1.99 | 23 |
| Woman, 65, 163 cm, 62 kg | 1.67 | 19 |
| Woman, 82, 157 cm, 48 kg | 1.45 | 17 |
| Man, 55, 175 cm, 118 kg | 2.40 | 28 |
What Changes at an eGFR of 20
20 is 5 points above 15, and a fall of about 30% would cross that line. Below 15, the result is in the kidney failure range (G5). It is already below 60 and 30.
9 of the 9 medicines in our registry whose labels use eGFR have a rule in force at 20. Compared with an eGFR of 25, one rule starts by 20: dapagliflozin (below the floor of 25 the registry gives for its kidney disease use).
| Medicine | At eGFR 20 | Next change if eGFR falls |
|---|---|---|
| Metformin | contraindicated | none lower in the registry |
| Sitagliptin | dose lowered to 25 mg | none lower in the registry |
| Saxagliptin | dose lowered to 2.5 mg | none lower in the registry |
| Dapagliflozin | glucose-lowering effect limited; below the floor of 25 the registry gives for its kidney disease use | none lower in the registry |
| Empagliflozin | glucose-lowering effect limited; other uses follow the indication | none lower in the registry |
| Canagliflozin | use limited; depends on the indication | none lower in the registry |
| Spironolactone | avoid | none lower in the registry |
| Hydrochlorothiazide | ineffective; the registry suggests a loop diuretic instead | none lower in the registry |
| Glyburide | avoid (CKD stage 3 to 5) | none lower in the registry |
These rows restate our renal dosing registry, which summarises the drug labels. Check the current label and the indication; the prescriber makes the dose decision.
Drug Dosing Cutoffs at eGFR 20
3 drugs in our renal dosing registry have a label cutoff at 20.
Labels That Use Creatinine Clearance
These labels use Cockcroft-Gault creatinine clearance in mL/min, not eGFR. An eGFR of 20 does not mean a clearance of 20 mL/min, so calculate CrCl before applying them.
- Dofetilide: CrCl below 20
- Levofloxacin: CrCl below 20
- Ofloxacin: CrCl below 20
The nearest other cutoffs are up at 25 (Acyclovir, Dapagliflozin) and down at 15 (8 drugs, listed under eGFR 15). Always confirm the current label, and leave the dose decision to the prescriber.
How a Result of 20 Is Confirmed
A result of 20 is confirmed by repeat testing over time, because one eGFR is a snapshot that can dip with dehydration or illness. Chronic kidney disease is diagnosed only when a low result, or kidney damage, lasts more than three months. Repeat testing, a urine albumin-to-creatinine ratio and, where muscle mass misleads, cystatin C confirm it.
When to Talk to Your Clinician
An eGFR of 20 should be reviewed promptly, usually with a kidney specialist, even if you feel well. Seek timely advice for swelling, a marked drop in urine output or new breathlessness, and have kidney function rechecked before and after any scan that uses contrast dye.
Nearby eGFR Results
Or browse all eGFR results. For drug dosing, your clinician may use a creatinine clearance rather than eGFR (see CrCl vs eGFR).