\
\
Lab Reference Library / eGFR (Estimated GFR)
Liver & Kidney
eGFR (Estimated GFR)
eGFR · Estimated Glomerular Filtration Rate · CKD-EPIReference range, optimal functional medicine levels, and why eGFR is the primary calculated measure of kidney filtration capacity, why values above 60 mL/min may still represent significant kidney function loss, and why cystatin C-based eGFR is more accurate than creatinine-based eGFR.
Kidney MarkerMost Searched
Standard RangeAbove 60 mL/min
FM OptimalAbove 90 mL/min
CKD Stage 3Below 60 mL/min
UnitsmL/min/1.73m²
\
← Back to Lab Reference Library
Category: Liver & Kidney | Also known as: Estimated Glomerular Filtration Rate, CKD-EPI eGFR | Sample: Calculated from serum creatinine (or cystatin C); not a direct measurement
1. What This Test Measures
eGFR (Estimated Glomerular Filtration Rate) is a calculated estimate of how much blood the kidneys filter per minute, standardized to a body surface area of 1.73 m² to allow comparison across different body sizes. It is derived from serum creatinine using validated mathematical equations that account for age, sex, and in some formulas, body weight, to correct for the known effects of these variables on creatinine production.
The most widely used equation is the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) creatinine equation, which replaced the older MDRD equation because it is more accurate across a wider range of GFR values, particularly in the normal and mildly reduced range above 60 mL/min/1.73m². A combined CKD-EPI creatinine-cystatin C equation is the most accurate readily available eGFR estimate and is increasingly recommended for confirmation when creatinine-based eGFR is borderline or when body composition makes creatinine unreliable.
eGFR is automatically calculated and reported whenever serum creatinine is ordered on a standard metabolic panel, making it the most widely available summary measure of kidney filtration capacity in clinical medicine. It is the primary metric used to stage chronic kidney disease (CKD) and to determine medication dose adjustments.
Important limitations of creatinine-based eGFR:
- Does not account for individual muscle mass variation; over-estimates GFR in sarcopenic individuals and under-estimates GFR in very muscular individuals
- Does not detect early kidney decline; creatinine (and therefore creatinine-based eGFR) does not change detectably until approximately 50 to 60% of filtration capacity is already lost
- The conventional threshold of "normal" at 60 mL/min/1.73m² does not reflect actual kidney health; a healthy young adult has eGFR of 120 to 130 mL/min/1.73m²
2. Why This Test Matters
- CKD staging and prognosis: eGFR is the primary metric for staging CKD from Stage 1 through Stage 5 (dialysis threshold). Each stage carries different treatment implications, monitoring frequency requirements, and cardiovascular risk levels. The combination of eGFR and urine albumin/creatinine ratio (ACR) provides the most complete kidney risk assessment.
- Medication dose adjustment: dozens of commonly prescribed medications require dose reduction or must be avoided entirely when eGFR falls below specific thresholds. Metformin is typically held at eGFR below 30. NSAIDs are avoided below 60. Many antibiotics, anticoagulants, and cardiac medications require dose adjustment based on eGFR. Failure to adjust for eGFR is a major source of medication toxicity in clinical practice.
- Cardiovascular risk stratification: reduced eGFR is an independent and powerful cardiovascular risk factor. At eGFR below 45, cardiovascular mortality risk exceeds kidney-specific mortality risk. The cardiovascular risk from reduced eGFR is comparable to having established coronary artery disease and is often underappreciated in standard cardiovascular risk calculations.
- Tracking kidney function over time: serial eGFR values reveal the rate of kidney function decline, which is clinically crucial. A decline of more than 5 mL/min/1.73m² per year is considered rapid progression and warrants urgent intervention. Stable eGFR over years, even at reduced absolute levels, has a much better prognosis than rapidly declining eGFR.
- Pre-procedure assessment: eGFR determines appropriateness of IV contrast administration (nephrologist guidance needed below 45), kidney biopsy risk stratification, and surgical risk assessment.
3. CKD Staging by eGFR
| CKD Stage | eGFR (mL/min/1.73m²) | Description | Monitoring Frequency |
|---|---|---|---|
| G1 | Above 90 (with damage) | Normal or high filtration with kidney damage marker | Annually |
| G2 | 60 to 89 (with damage) | Mildly decreased | Annually |
| G3a | 45 to 59 | Mildly to moderately decreased | Every 6 months |
| G3b | 30 to 44 | Moderately to severely decreased | Every 3 to 6 months |
| G4 | 15 to 29 | Severely decreased | Every 3 months; nephrology |
| G5 | Below 15 | Kidney failure | Dialysis planning |
CKD requires kidney damage markers (proteinuria, hematuria, abnormal imaging) OR eGFR below 60 for 3 or more months. Stage 1 and 2 CKD require both reduced eGFR AND a kidney damage marker. Albuminuria (urine ACR) is the most sensitive damage marker and amplifies risk at any eGFR level.
4. Optimal Functional Medicine eGFR
| eGFR | Functional Interpretation |
|---|---|
| Above 100 | Excellent: full filtration capacity; lowest metabolic and cardiovascular risk from kidney standpoint |
| 90 to 100 | Optimal: normal kidney function; age-appropriate for adults under 50 |
| 75 to 89 | Good: mild decline from expected young-adult baseline; address risk factors; annual monitoring |
| 60 to 74 | Moderate concern: meaningful filtration loss relative to baseline; aggressive risk factor management |
| Below 60 | CKD Stage 3 or above: nephrology involvement; intensified cardiovascular risk management |
5. Why eGFR Above 60 Is Not Always Reassuring
The baseline problem: a healthy young adult typically has eGFR of 120 to 130 mL/min/1.73m². An eGFR of 65 mL/min/1.73m² in a 42-year-old represents approximately 50% loss of expected filtration capacity, even though the CKD threshold of 60 has not been crossed and the lab report may not flag any abnormality. By the time the conventional normal/abnormal line at 60 is crossed, the kidney has already lost 50 to 60% of its functional capacity relative to expected young-adult levels.
In functional medicine, we track the trajectory and compare to age-expected values, not just whether the result is above or below 60 mL/min/1.73m². A 45-year-old with an eGFR of 68 trending down 5 mL/min per year needs the same aggressive intervention as one with eGFR of 58.
6. What Causes Declining eGFR
- Diabetes mellitus: the single leading cause of CKD in developed countries; hyperglycemia damages glomerular basement membrane and promotes hyperfiltration injury followed by progressive nephron loss; early detection with microalbuminuria testing is critical
- Hypertension: second most common cause; chronically elevated blood pressure damages afferent arterioles and glomeruli; even prehypertension is associated with accelerated eGFR decline
- Aging (physiological): eGFR declines approximately 1 mL/min/1.73m² per year after age 40 as part of normal aging; a 70-year-old may have eGFR of 70 mL/min/1.73m² purely from aging without any disease
- Glomerulonephritis: immune-mediated inflammation of the glomeruli from IgA nephropathy, lupus nephritis, membranous nephropathy, and other conditions; proteinuria is the hallmark; specialist management required
- NSAID use: chronic NSAID use reduces prostaglandin-mediated afferent arteriolar dilation, chronically reducing GFR; important reversible cause of eGFR decline
- Recurrent acute kidney injury: each AKI episode causes permanent nephron loss; repeated episodes from dehydration, infection, contrast, or medications accelerate CKD progression
- Hyperuricemia: uric acid causes tubulointerstitial nephritis and promotes afferent arteriolar vasoconstriction; target uric acid below 5.5 mg/dL in CKD patients
- Obesity: causes glomerular hyperfiltration initially (eGFR may appear high), followed by nephron burnout and progressive eGFR decline
7. How to Preserve eGFR
Blood Pressure and Glucose
- Blood pressure target: below 130/80 mmHg; below 120/80 mmHg with proteinuria; ACE inhibitors and ARBs are first-line for their antiproteinuric and renoprotective effects beyond blood pressure
- SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin): now have Level 1 evidence for kidney protection in CKD with and without diabetes; slow eGFR decline by reducing glomerular hyperfiltration through tubuloglomerular feedback; reduce cardiovascular mortality in CKD
- Blood sugar control: HbA1c below 7% for diabetic kidney disease; avoid hypoglycemia in advanced CKD (kidneys produce glucose through gluconeogenesis)
- GLP-1 receptor agonists (semaglutide): emerging evidence for kidney protection through anti-inflammatory and cardiovascular mechanisms
Nephrotoxin Avoidance
- Eliminate chronic NSAID use: NSAIDs reduce prostaglandin-mediated GFR support; switch to acetaminophen (with dose awareness) or non-pharmacological analgesia
- Manage contrast agent exposure: pre-hydrate, minimize contrast volume, consider isoosmolar contrast agents for eGFR below 45
- Avoid aminoglycoside antibiotics unless no alternatives; monitor drug levels carefully when required
- Long-term PPI use: associated with tubulointerstitial nephritis and CKD; reassess necessity regularly
- Stop herbal nephrotoxins: aristolochic acid (in some traditional Chinese herbs), chromium picolinate in excessive doses
Nutrition and Supplements
- Protein optimization: for eGFR above 30, 0.8 to 1.0g/kg daily is appropriate; below 30, modest restriction to 0.6 to 0.8g/kg slows progression; avoid extreme restriction (below 0.6g/kg) due to malnutrition risk
- Adequate hydration: 2 to 3 liters of water daily; dehydration is an underappreciated accelerant of CKD progression
- Sodium restriction (below 2,000mg daily): reduces blood pressure and proteinuria
- Omega-3 fatty acids (2 to 4g EPA and DHA daily): anti-inflammatory; slows CKD progression in IgA nephropathy
- Uric acid management (below 5.5 mg/dL): vitamin C, tart cherry, dietary fructose restriction, and allopurinol when indicated
- Bicarbonate supplementation in metabolic acidosis (CKD Stage 3 and above): slows CKD progression by reducing ammonia-mediated tubulointerstitial injury
8. The Complete Kidney Panel: Pattern Interpretation
eGFR is the central organizing value of the kidney panel. The complete pattern adds critical nuance:
| eGFR (CKD-EPI Cr) | CysC | SDMA | Urine ACR | CKD Stage | Priority Action |
|---|---|---|---|---|---|
| Above 90 | Below 0.90 | Below 0.50 | Below 30 | No CKD | Annual monitoring; address metabolic risk factors |
| 60 to 89 | 0.90 to 1.10 | 0.50 to 0.65 | Below 30 | Stage 2 (with damage marker) | Aggressive risk factor management; 6-month monitoring |
| 45 to 59 | 1.10 to 1.30 | 0.65 to 0.80 | Any | Stage 3a | Nephrology co-management; cardiovascular risk very high |
| Above 90 (Cr-based) | Above 1.00 | Above 0.55 | 30 to 300 | Stage 1 CKD (damage present) | CysC and SDMA detect early decline creatinine misses; microalbuminuria is key |
| 60 to 75 (Cr-based) | Below 0.90 | Below 0.50 | Below 30 | Muscle mass artifact | High creatinine from muscle mass; CysC and SDMA confirm true GFR is normal |
9. Related Lab Tests
CreatinineInput Variable for eGFR Calculation
→
Cystatin CMore Accurate eGFR Without Muscle Bias
→
SDMADetects Decline Before eGFR Becomes Abnormal
→
BUNBUN/Cr Ratio for Cause Differentiation
→
Uric AcidAccelerates CKD; Target Below 5.5
→
HbA1cDiabetes: Leading Cause of Declining eGFR
→
10. When Testing Is Recommended
- eGFR is automatically reported with every serum creatinine; evaluate with every standard metabolic panel
- Diabetes and hypertension: at minimum annual eGFR monitoring; more frequently as eGFR declines
- CKD Stage 3 and above: every 3 to 6 months depending on stage and stability
- Before initiating or continuing metformin, NSAIDs, certain antibiotics, contrast agents, or other renally-cleared medications
- Any functional medicine longevity panel: eGFR is a primary aging biomarker
- Monitoring response to SGLT2 inhibitors, blood pressure management, and other kidney-protective interventions
- Any patient with cystatin C or SDMA above optimal: track eGFR trend alongside more sensitive markers
11. Clinical Perspective
Clinical Perspective
The number that bothers me most in clinical medicine is the 65-year-old whose eGFR is 62 and the lab report says normal. It is not normal. At 65, expected eGFR from aging alone should still be around 80 to 85. An eGFR of 62 at that age means the kidneys have lost roughly 40% of expected function, and if there is diabetes or hypertension or a few years of NSAID use in the history, some of that loss is from avoidable causes. What we should be doing at eGFR 75 or 80 is aggressively managing blood pressure, eliminating NSAIDs, considering SGLT2 inhibitors, checking cystatin C and SDMA, looking for microalbuminuria, and having a serious conversation about trajectory. The CKD threshold at 60 is a line drawn for diagnostic clarity, not a dividing line between kidney health and kidney disease.
Brian Lamkin, DO | Founder, The Lamkin Clinic | Edmond, Oklahoma
12. Frequently Asked Questions
What is the optimal eGFR?
In functional medicine, optimal eGFR is above 90 mL/min/1.73m², corresponding to normal or near-normal kidney filtration capacity. The conventional CKD threshold of 60 mL/min/1.73m² represents a point where significant filtration capacity has already been lost. A young healthy adult has eGFR of 120 to 130 mL/min/1.73m², so an eGFR of 65 in a 45-year-old represents approximately 50% loss of expected function even though it is above the diagnostic CKD threshold.
What are the CKD stages by eGFR?
CKD stages by eGFR: G1 above 90 with kidney damage marker, G2 60 to 89 with kidney damage, G3a 45 to 59, G3b 30 to 44, G4 15 to 29, G5 below 15 (kidney failure). Albuminuria (urine ACR) amplifies risk at any eGFR stage: a patient with eGFR 65 and urine ACR above 300 mg/g has much higher risk than one with the same eGFR and normal urine ACR.
Why is eGFR above 60 not always reassuring?
A young healthy adult has eGFR of 120 to 130 mL/min/1.73m². An eGFR of 65 in a 42-year-old represents approximately 50% loss of expected filtration capacity, even though the CKD threshold of 60 has not been crossed. The conventional normal/abnormal line at 60 does not account for baseline expected GFR by age. Serial eGFR trends and comparison to age-expected values are essential for proper interpretation.
What is the difference between creatinine-based and cystatin C-based eGFR?
Creatinine-based eGFR is affected by muscle mass, making it overestimate GFR in very muscular individuals and underestimate GFR in sarcopenic elderly. Cystatin C-based eGFR is not affected by muscle mass or diet and more accurately reflects true GFR across all body types. The combined CKD-EPI creatinine-cystatin C equation is the most accurate readily available eGFR estimate and is recommended when body composition makes creatinine-based eGFR unreliable.
What slows CKD progression?
The most evidence-based interventions are: blood pressure control below 130/80 mmHg with ACE inhibitors or ARBs as first-line; SGLT2 inhibitors (empagliflozin, dapagliflozin) which have Level 1 evidence for kidney protection in CKD with and without diabetes; blood sugar control in diabetic kidney disease; elimination of NSAIDs; adequate hydration; uric acid management; sodium restriction; and omega-3 fatty acids in inflammatory nephropathy.
Content authored and clinically reviewed by Brian Lamkin, DO, founder of The Lamkin Clinic in Edmond, Oklahoma. Brian Lamkin, DO has 25+ years of experience in functional and regenerative medicine. This page reflects current functional medicine practice standards and is updated as new clinical evidence becomes available.
An eGFR above 60 is not a clean bill of kidney health. It is a starting point for a conversation about trajectory.
A complete kidney panel with cystatin C, SDMA, urine albumin, and eGFR trends reveals what a single creatinine cannot. Schedule a consultation for comprehensive kidney function assessment.
Schedule a ConsultationMedical Disclaimer: This content is provided for educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Lab interpretation should always be performed in clinical context by a qualified healthcare provider. Reference ranges and optimal targets may vary based on individual patient history, clinical presentation, and laboratory methodology. Schedule a consultation to discuss your specific results with Dr. Lamkin.