What does low eGFR mean?
Low eGFR indicates reduced kidney function, with values below 60 mL/min/1.73m² suggesting chronic kidney disease. Early detection through regular testing allows for interventions to slow progression and protect kidney health.
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Understanding eGFR and Kidney Function
The estimated glomerular filtration rate (eGFR) is one of the most important indicators of kidney health. This calculation estimates how well your kidneys filter waste and excess fluid from your blood. Think of your kidneys as sophisticated filtration systems that work around the clock to clean your blood, remove toxins, and maintain the delicate balance of minerals and fluids in your body.
Your eGFR is calculated using a formula that considers your blood creatinine level, age, sex, and sometimes race. Creatinine is a waste product from muscle metabolism that healthy kidneys filter out efficiently. When kidney function declines, creatinine builds up in the blood, leading to a lower eGFR calculation.
A normal eGFR is typically above 90 mL/min/1.73m², though values above 60 are generally considered acceptable if there are no other signs of kidney damage. When eGFR drops below 60, it indicates that kidney function has declined to a level that requires attention and monitoring. Understanding your eGFR levels through regular testing can help catch kidney problems early when interventions are most effective.
eGFR Stages and Clinical Significance
| eGFR Range (mL/min/1.73m²) | Stage | Kidney Function | Clinical Action | |
|---|---|---|---|---|
| ≥90 | ≥90 | Stage 1 | Normal or high | Monitor if other kidney damage signs present |
| 60-89 | 60-89 | Stage 2 | Mildly decreased | Monitor annually, control risk factors |
| 45-59 | 45-59 | Stage 3a | Mild to moderately decreased | Monitor every 6 months, refer to nephrologist |
| 30-44 | 30-44 | Stage 3b | Moderately to severely decreased | Monitor every 3 months, prepare for kidney replacement |
| 15-29 | 15-29 | Stage 4 | Severely decreased | Prepare for dialysis or transplant |
| <15 | <15 | Stage 5 | Kidney failure | Dialysis or kidney transplant needed |
eGFR stages help guide treatment decisions and monitoring frequency. Always interpret with other clinical findings.
What Low eGFR Values Mean
Low eGFR values are categorized into stages that help healthcare providers understand the severity of kidney dysfunction and guide treatment decisions. Understanding these stages can help you grasp what your test results mean for your health.
Interpreting Your Results
An eGFR between 60-89 mL/min/1.73m² may indicate mild kidney function loss, especially if accompanied by other signs of kidney damage like protein in the urine. While this range doesn't always require treatment, it signals the need for monitoring and preventive measures.
When eGFR falls below 60 mL/min/1.73m², it indicates moderate to severe kidney disease. At this stage, waste products begin accumulating in the blood, potentially causing symptoms and complications. An eGFR below 15 indicates kidney failure, requiring dialysis or transplantation.
Factors Affecting eGFR Accuracy
Several factors can influence eGFR calculations and should be considered when interpreting results:
- Muscle mass: Very muscular individuals may have higher creatinine levels, potentially underestimating eGFR
- Age: eGFR naturally declines with age, approximately 1 mL/min/1.73m² per year after age 40
- Pregnancy: Can temporarily affect kidney function and eGFR calculations
- Medications: Certain drugs can affect creatinine levels or kidney function
- Recent high-protein meals: Can temporarily elevate creatinine
Common Causes of Low eGFR
Understanding what causes eGFR to drop can help you identify risk factors and take preventive action. Kidney function can decline due to various acute and chronic conditions.
Chronic Conditions
Diabetes is the leading cause of chronic kidney disease, accounting for about 40% of cases. High blood sugar damages the small blood vessels in the kidneys over time, reducing their filtering capacity. Similarly, high blood pressure is responsible for about 25% of kidney disease cases, as elevated pressure damages kidney blood vessels.
Other chronic conditions that can lower eGFR include:
- Polycystic kidney disease: A genetic disorder causing cysts to form in the kidneys
- Glomerulonephritis: Inflammation of the kidney's filtering units
- Autoimmune diseases: Such as lupus or IgA nephropathy
- Chronic urinary tract infections or kidney stones
- Heart disease: Poor cardiac function can reduce kidney blood flow
Acute Causes
Sometimes eGFR can drop suddenly due to acute kidney injury. This might result from severe dehydration, certain medications (like NSAIDs or some antibiotics), severe infections, or exposure to contrast dyes used in medical imaging. Unlike chronic kidney disease, acute kidney injury may be reversible with prompt treatment.
Symptoms of Low eGFR
Early kidney disease often progresses silently, which is why regular testing is crucial. Many people with moderately reduced eGFR (stage 2-3 kidney disease) experience no symptoms at all. However, as kidney function continues to decline, various symptoms may emerge.
Early Warning Signs
In the earlier stages of kidney dysfunction, you might notice:
- Fatigue and weakness due to anemia from reduced erythropoietin production
- Changes in urination patterns, including increased frequency, especially at night
- Foamy or bubbly urine indicating protein leakage
- Mild swelling in the legs, ankles, or feet
- High blood pressure that's difficult to control
Advanced Symptoms
As eGFR drops below 30 mL/min/1.73m², more severe symptoms typically develop:
- Persistent nausea and vomiting
- Loss of appetite and unintentional weight loss
- Metallic taste in the mouth
- Severe fatigue and difficulty concentrating
- Muscle cramps and twitching
- Persistent itching (pruritus)
- Shortness of breath from fluid buildup
- Chest pain if fluid accumulates around the heart
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Testing and Monitoring Your eGFR
Regular monitoring of kidney function is essential, especially if you have risk factors like diabetes, hypertension, or a family history of kidney disease. The eGFR test is typically part of a comprehensive metabolic panel or can be ordered specifically to assess kidney function.
When to Get Tested
The National Kidney Foundation recommends annual eGFR testing for people with:
- Diabetes or prediabetes
- High blood pressure
- Heart disease
- Family history of kidney disease
- Age over 60
- History of acute kidney injury
- Regular use of medications that can affect kidneys
If you have existing kidney disease, your doctor may recommend testing every 3-6 months to monitor progression. Regular monitoring allows for timely interventions and helps track the effectiveness of treatments. Comprehensive metabolic testing that includes eGFR, along with other kidney function markers, provides the most complete picture of your kidney health.
Additional Kidney Function Tests
While eGFR is a crucial marker, other tests provide complementary information about kidney health:
- Urine albumin-to-creatinine ratio (ACR): Detects protein leakage
- Blood urea nitrogen (BUN): Another waste product filtered by kidneys
- Cystatin C: An alternative marker for estimating GFR
- Kidney ultrasound or CT scan: To visualize kidney structure
- Kidney biopsy: In some cases, to determine the exact cause of kidney disease
Improving and Protecting Kidney Function
While some kidney damage may be irreversible, many interventions can slow progression and even improve kidney function in certain cases. The key is early detection and consistent management of underlying conditions.
Lifestyle Modifications
Diet plays a crucial role in kidney health. A kidney-friendly diet typically includes:
- Limiting sodium to less than 2,300 mg daily to control blood pressure
- Moderating protein intake, especially from animal sources
- Choosing whole grains and limiting processed foods
- Eating plenty of fruits and vegetables (with some restrictions in advanced kidney disease)
- Staying well-hydrated unless fluid restrictions are prescribed
- Limiting phosphorus and potassium if levels are elevated
Regular physical activity improves cardiovascular health and helps control blood pressure and blood sugar, both crucial for kidney protection. Aim for at least 150 minutes of moderate-intensity exercise weekly. Weight management is also important, as obesity increases the risk of diabetes and hypertension.
Medical Management
Controlling underlying conditions is paramount for preserving kidney function. This includes:
- Blood pressure control: Target typically below 130/80 mmHg
- Blood sugar management: HbA1c below 7% for most people with diabetes
- Medications: ACE inhibitors or ARBs to protect kidneys
- Cholesterol management: Statins may be prescribed
- Avoiding nephrotoxic medications when possible
- Regular monitoring and medication adjustments
When to Seek Medical Attention
Certain situations warrant immediate medical attention, even if you're already being monitored for kidney disease. Seek urgent care if you experience:
- Sudden decrease in urination or inability to urinate
- Severe swelling in legs, ankles, or around eyes
- Shortness of breath or chest pain
- Severe nausea and vomiting
- Confusion or difficulty concentrating
- Severe fatigue or weakness
- Blood in urine or very dark urine
Additionally, schedule an appointment with your healthcare provider if your home blood pressure readings are consistently elevated, you notice persistent changes in urination patterns, or you develop new symptoms that could indicate worsening kidney function.
Living Well with Reduced eGFR
A diagnosis of reduced kidney function can feel overwhelming, but many people live full, active lives while managing kidney disease. The key is taking a proactive approach to your health through regular monitoring, lifestyle modifications, and working closely with your healthcare team.
Remember that kidney disease progression isn't inevitable. With proper management, many people maintain stable kidney function for years or even decades. Focus on what you can control: maintaining a healthy lifestyle, taking medications as prescribed, attending regular check-ups, and staying informed about your condition.
Consider joining a support group or working with a kidney disease educator to better understand your condition and connect with others facing similar challenges. Knowledge and support are powerful tools in managing kidney health effectively.
References
- Levey, A. S., Stevens, L. A., Schmid, C. H., et al. (2009). A new equation to estimate glomerular filtration rate. Annals of Internal Medicine, 150(9), 604-612.[PubMed][DOI]
- KDIGO CKD Work Group. (2024). KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney International, 105(4S), S117-S314.[Link][DOI]
- Grams, M. E., Chow, E. K., Segev, D. L., & Coresh, J. (2013). Lifetime incidence of CKD stages 3-5 in the United States. American Journal of Kidney Diseases, 62(2), 245-252.[PubMed][DOI]
- Chen, T. K., Knicely, D. H., & Grams, M. E. (2019). Chronic Kidney Disease Diagnosis and Management: A Review. JAMA, 322(13), 1294-1304.[PubMed][DOI]
- Kalantar-Zadeh, K., Jafar, T. H., Nitsch, D., Neuen, B. L., & Perkovic, V. (2021). Chronic kidney disease. The Lancet, 398(10302), 786-802.[PubMed][DOI]
- Webster, A. C., Nagler, E. V., Morton, R. L., & Masson, P. (2017). Chronic Kidney Disease. The Lancet, 389(10075), 1238-1252.[PubMed][DOI]
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