eGFR (estimated glomerular filtration rate) measures how well kidneys filter blood per minute. Calculated from serum creatinine using equations that account for age and sex; the 2021 CKD-EPI equation replaced the previous version that included a race adjustment. Normal eGFR is ≥90 mL/min/1.73 m²; CKD is diagnosed at less than 60 for 3+ months. eGFR is the most commonly used measure of kidney function in clinical practice. CKD staging: Stage 1 (eGFR ≥90 with kidney damage), Stage 2 (60-89), Stage 3a (45-59), Stage 3b (30-44), Stage 4 (15-29), Stage 5 (less than 15, dialysis or transplant). Diabetes is the leading cause of kidney disease in the U.S. — about 40% of adults on dialysis have diabetes. Diabetic nephropathy typically progresses: microalbuminuria → macroalbuminuria → declining eGFR → kidney failure. Annual eGFR monitoring detects early decline; aggressive intervention can slow or stabilize progression. Many diabetes medications require dose adjustment based on eGFR: metformin (full dose if eGFR ≥45, reduced 30-45, contraindicated under 30), SGLT2 inhibitors (eGFR ≥20-25 acceptable), sulfonylureas (glipizide preferred), DPP-4 inhibitors (most need adjustment; linagliptin doesn’t), GLP-1 agonists (generally safe), insulin (may need less in CKD due to slower clearance).
CKD Staging by eGFR
| Stage | eGFR (mL/min/1.73 m²) | Description | Action |
|---|---|---|---|
| 1 | ≥90 | Normal function + kidney damage | Annual monitoring; treat damage |
| 2 | 60-89 | Mild reduction | Annual monitoring; assess progression |
| 3a | 45-59 | Mild-moderate reduction | Address risk factors; medication review |
| 3b | 30-44 | Moderate-severe reduction | Nephrology consult; dose adjust meds |
| 4 | 15-29 | Severe reduction | Nephrology care; prepare for replacement therapy |
| 5 | under 15 | Kidney failure | Dialysis or transplant |
Diabetes Medication Dosing by eGFR
| Medication | eGFR ≥60 | eGFR 30-59 | eGFR under 30 |
|---|---|---|---|
| Metformin | Standard dose | Reduced dose | Contraindicated |
| Empagliflozin (Jardiance) | Standard | Standard until 20 | Discontinue under 20 |
| Dapagliflozin (Farxiga) | Standard | Standard until 25 | Discontinue under 25 |
| Canagliflozin (Invokana) | Standard | Standard if eGFR ≥30 | Discontinue |
| Sitagliptin (Januvia) | 100 mg | 50 mg | 25 mg |
| Linagliptin (Tradjenta) | Standard | Standard | Standard |
| Glipizide | Preferred sulfonylurea | Preferred | Use with caution |
| Glyburide | OK | Avoid | Avoid |
| Semaglutide (Ozempic) | OK | OK | OK |
| Insulin | OK | May need less | May need less |
Why Diabetes Causes Kidney Disease
- Chronic hyperglycemia damages glomerular capillary walls.
- Hyperfiltration in early diabetes overworks kidneys.
- Hypertension (common with diabetes) damages blood vessels.
- Inflammation accelerates damage.
- Advanced glycation end products (AGEs) deposit in kidneys.
- Renin-angiotensin-aldosterone system activation.
- Genetic susceptibility varies among adults.
- Risk factors: longer diabetes duration, poor glucose control, hypertension, smoking, family history.
Slowing Progression
- Glucose control: A1C under 7% (individualize based on comorbidities).
- Blood pressure control: under 130/80 mmHg.
- ACE inhibitor or ARB: first-line if microalbuminuria or hypertension.
- SGLT2 inhibitor: kidney protection demonstrated in CREDENCE, DAPA-CKD, EMPA-KIDNEY.
- Finerenone (Kerendia): nonsteroidal MR antagonist for T2D + CKD.
- GLP-1 agonist: modest kidney benefit.
- Weight loss: 5-10% improves multiple risk factors.
- Smoking cessation: significantly reduces progression.
- Sodium reduction: under 2.3 g daily.
- Protein moderation: 0.8 g/kg body weight if not malnourished.
- Avoid NSAIDs: ibuprofen, naproxen damage kidneys.
- Avoid contrast media when possible: discuss with provider before scans.
2021 Race-Free eGFR Equation
- Prior CKD-EPI equation included race-based adjustment (Black race coefficient).
- 2021 CKD-EPI equation removes race adjustment.
- Changes were made because race is a social construct, not biological.
- Race-free equation slightly increases eGFR estimates for Black adults compared with prior equation.
- May affect medication dose adjustments and CKD staging classifications.
- Cystatin C-based eGFR equation is more accurate but less widely available.
- Most labs in U.S. have adopted 2021 equation.
- Discuss with provider if recent change in calculated eGFR appears.
When to See a Nephrologist
- eGFR consistently under 45.
- Rapid eGFR decline (over 5 mL/min/year).
- Persistent macroalbuminuria (ACR over 300).
- Difficult-to-control hypertension.
- Resistant hyperkalemia.
- Suspected non-diabetic kidney disease.
- Preparation for dialysis (eGFR under 30).
- Kidney transplant evaluation.
- Difficult cases for primary care to manage alone.
The Bottom Line
eGFR measures kidney function — how well kidneys filter blood per minute. Calculated from serum creatinine using equations accounting for age and sex; the 2021 CKD-EPI equation replaced the prior race-based version. Normal eGFR is ≥90; CKD is diagnosed at less than 60 for 3+ months. CKD staging: Stage 1 (eGFR ≥90 with kidney damage), Stage 2 (60-89), Stage 3a (45-59), Stage 3b (30-44), Stage 4 (15-29), Stage 5 (under 15, dialysis or transplant). Diabetes is the leading cause of kidney disease in the U.S. — about 40% of adults on dialysis have diabetes. Diabetic nephropathy typically progresses: microalbuminuria → macroalbuminuria → declining eGFR → kidney failure. Annual eGFR monitoring detects early decline; aggressive intervention can slow or stabilize progression. Critical medication dosing implications: metformin (full dose if eGFR ≥45, reduced 30-45, contraindicated under 30), SGLT2 inhibitors (most can continue down to eGFR 20-25), sulfonylureas (glipizide preferred over glyburide in CKD), DPP-4 inhibitors (most need adjustment; linagliptin doesn’t), GLP-1 agonists (generally safe), insulin (may need less in CKD due to slower clearance — monitor for hypoglycemia). Slowing progression: glucose control (A1C under 7%), blood pressure control (under 130/80), ACE inhibitor or ARB (first-line), SGLT2 inhibitor (kidney protection from CREDENCE, DAPA-CKD, EMPA-KIDNEY trials), finerenone (Kerendia) for T2D + CKD, GLP-1 agonist (modest benefit), weight loss, smoking cessation, sodium reduction, modest protein moderation, avoid NSAIDs (ibuprofen, naproxen damage kidneys), avoid unnecessary contrast media. Nephrology referral for eGFR under 45, rapid decline (over 5/year), persistent macroalbuminuria, difficult hypertension, or preparing for dialysis. For adults with type 2 diabetes, annual eGFR monitoring is essential alongside microalbumin testing; early detection enables interventions that preserve kidney function and prevent dialysis. See our broader nephropathy guide for context.
