Is very high eGFR normal?
A very high eGFR (over 90-120 mL/min/1.73m²) is generally normal and indicates healthy kidney function, though extremely high values may warrant investigation. Most labs don't report exact values above 60-90 as the test becomes less accurate at higher ranges.
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What is eGFR and Why Does It Matter?
The estimated glomerular filtration rate (eGFR) is one of the most important tests for assessing kidney function. It estimates how much blood your kidneys filter each minute, essentially measuring how well they're doing their job of removing waste products and excess fluid from your body.
Unlike many health markers where both high and low values can be problematic, eGFR is unique. A high eGFR typically indicates that your kidneys are functioning well, while a low eGFR suggests kidney damage or disease. This makes understanding your eGFR results crucial for monitoring your overall health and catching potential kidney issues early.
If you're interested in monitoring your kidney function along with other vital health markers, comprehensive testing can provide valuable insights into your metabolic health.
eGFR Ranges and Their Clinical Significance
| eGFR Range (mL/min/1.73m²) | Kidney Function Stage | Clinical Interpretation | Recommended Action | |
|---|---|---|---|---|
| >90 | >90 | Stage 1 (if kidney damage present) or Normal | Normal kidney function | Continue healthy lifestyle, annual monitoring |
| 60-89 | 60-89 | Stage 2 | Mild decrease in kidney function | Monitor every 6-12 months, manage risk factors |
| 30-59 | 30-59 | Stage 3 | Moderate decrease in kidney function | See nephrologist, monitor every 3-6 months |
| 15-29 | 15-29 | Stage 4 | Severe decrease in kidney function | Prepare for kidney replacement therapy |
| <15 | <15 | Stage 5 | Kidney failure | Requires dialysis or transplant |
eGFR stages are based on National Kidney Foundation guidelines. Values should be interpreted alongside other clinical findings.
Understanding Normal eGFR Ranges
Normal eGFR values vary based on age, sex, and body size, but generally fall within these ranges:
- 90-120 mL/min/1.73m² or higher: Normal kidney function
- 60-89 mL/min/1.73m²: Mild decrease in kidney function
- 30-59 mL/min/1.73m²: Moderate decrease in kidney function
- 15-29 mL/min/1.73m²: Severe decrease in kidney function
- Less than 15 mL/min/1.73m²: Kidney failure
It's important to note that eGFR naturally declines with age. A healthy 20-year-old might have an eGFR of 116 mL/min/1.73m², while a healthy 70-year-old might have an eGFR of 75 mL/min/1.73m². This age-related decline is normal and doesn't necessarily indicate kidney disease.
Understanding these ranges helps put your results in context.
When High eGFR is Actually Normal
In most cases, a very high eGFR is completely normal and indicates healthy, well-functioning kidneys. Many laboratories don't even report exact values above 60 or 90 mL/min/1.73m² because the calculation becomes less accurate at higher ranges. Instead, they simply report results as ">60" or ">90," which essentially means "normal."
Why Labs Don't Report Exact High Values
The eGFR calculation uses creatinine levels, age, sex, and race to estimate kidney function. However, this formula becomes less precise at higher filtration rates. Small variations in creatinine can cause large swings in the calculated eGFR when kidney function is normal or near-normal. This is why many labs cap their reporting at 60 or 90 mL/min/1.73m².
Factors That Can Increase eGFR
Several benign factors can lead to higher eGFR readings:
- Being younger (kidney function naturally declines with age)
- Having lower muscle mass (which produces less creatinine)
- Pregnancy (increased blood flow to kidneys)
- High protein diet consumed before testing
- Certain medications that affect creatinine levels
When to Be Concerned About Very High eGFR
While high eGFR is generally good news, there are rare situations where an extremely high value might warrant further investigation. If your lab reports an exact eGFR value above 120-140 mL/min/1.73m², it could indicate:
Hyperfiltration
Hyperfiltration occurs when the kidneys are working harder than normal to filter blood. This can happen in the early stages of diabetes or hypertension, where the kidneys compensate for metabolic stress by increasing their filtration rate. While this might seem beneficial, prolonged hyperfiltration can actually damage the kidneys over time.
Laboratory or Calculation Errors
Sometimes, very high eGFR values result from laboratory errors or issues with the calculation formula. This is more likely if:
- You have very low muscle mass
- You're taking medications that interfere with creatinine measurements
- There was an error in recording your age, sex, or race
- The blood sample was improperly handled
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Other Kidney Function Tests to Consider
While eGFR is an excellent screening tool, it's not the only way to assess kidney health. If you have concerns about your kidney function or want a more complete picture, consider these additional tests:
- Creatinine: The building block of eGFR calculations
- Blood Urea Nitrogen (BUN): Another waste product filtered by kidneys
- Cystatin C: An alternative marker that's less affected by muscle mass
- Urine albumin: Detects protein in urine, an early sign of kidney damage
- Urine creatinine ratio: Helps assess kidney function more accurately
Regular monitoring of these markers can help you track your kidney health over time and catch any changes early.
Lifestyle Factors That Support Healthy Kidney Function
Whether your eGFR is high, normal, or concerning, maintaining healthy kidneys should be a priority. Your kidneys work 24/7 to filter waste, regulate blood pressure, and maintain fluid balance. Here's how to keep them functioning optimally:
Stay Hydrated
Adequate hydration helps your kidneys flush out toxins and waste products. Aim for 6-8 glasses of water daily, adjusting for activity level and climate. However, avoid overhydration, which can strain your kidneys.
Manage Blood Pressure and Blood Sugar
High blood pressure and diabetes are the leading causes of kidney disease. Keep your blood pressure below 120/80 mmHg and maintain healthy blood sugar levels through diet, exercise, and medication if needed.
Limit Sodium and Processed Foods
Excessive sodium makes your kidneys work harder and can damage blood vessels. Aim for less than 2,300 mg of sodium daily and focus on whole, unprocessed foods.
When to Retest Your eGFR
The frequency of eGFR testing depends on your overall health and risk factors. Here are general guidelines:
- Healthy adults: Every 1-2 years as part of routine check-ups
- People with diabetes or hypertension: Every 6-12 months
- Those with known kidney disease: Every 3-6 months or as directed
- After starting new medications: Within 1-2 weeks to check for effects
If you receive an unusually high or low eGFR result, your healthcare provider may recommend retesting to confirm the findings, especially if the result doesn't match your clinical picture.
The Bottom Line on High eGFR
A very high eGFR is typically a sign of healthy kidneys and nothing to worry about. In fact, it's what we want to see! Most labs don't even report exact values above 60-90 mL/min/1.73m² because the test isn't designed to be precise at high levels of kidney function.
However, if you're seeing extremely high values (above 120-140 mL/min/1.73m²) or have other concerning symptoms, it's worth discussing with your healthcare provider. They can help determine if additional testing is needed or if other factors might be affecting your results.
Remember, kidney health is best assessed through multiple markers over time, not a single test result. Regular monitoring, combined with a healthy lifestyle, gives you the best chance of maintaining optimal kidney function throughout your life.
References
- Levey AS, Stevens LA, Schmid CH, et al. A new equation to estimate glomerular filtration rate. Ann Intern Med. 2009;150(9):604-612.[PubMed][DOI]
- Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int Suppl. 2013;3(1):1-150.[Link]
- Inker LA, Astor BC, Fox CH, et al. KDOQI US commentary on the 2012 KDIGO clinical practice guideline for the evaluation and management of CKD. Am J Kidney Dis. 2014;63(5):713-735.[PubMed][DOI]
- Glassock RJ, Winearls C. Screening for CKD with eGFR: doubts and dangers. Clin J Am Soc Nephrol. 2008;3(5):1563-1568.[PubMed][DOI]
- Delanaye P, Jager KJ, Bökenkamp A, et al. CKD: A Call for an Age-Adapted Definition. J Am Soc Nephrol. 2019;30(10):1785-1805.[PubMed][DOI]
- Tonelli M, Riella M. Chronic kidney disease and the aging population. World Kidney Day Steering Committee. Kidney Int. 2014;85(3):487-491.[PubMed][DOI]
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