The Estimated Glomerular Filtration Rate (eGFR) is a calculated number that measures how effectively your kidneys are working. Kidneys filter waste and excess fluid from the blood, and the eGFR estimates this clearance rate. This measurement is important for healthcare professionals to screen for, detect, and monitor kidney dysfunction over time. A lower eGFR indicates less efficient filtering, prompting further investigation and the development of a care plan.
Understanding Your eGFR Score
The eGFR is an estimate derived from a blood test measuring creatinine, a waste product from muscle breakdown. This creatinine level is entered into a mathematical formula, typically the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, along with your age and sex. Clinical guidelines have moved away from incorporating race to ensure equitable assessment of kidney function.
The eGFR value is reported in milliliters per minute per 1.73 square meters of body surface area. This number is used to stage Chronic Kidney Disease (CKD), with a higher score signifying better function. For adults, an eGFR of 90 or greater is considered normal, assuming no other signs of kidney damage, such as protein in the urine.
The CKD staging system classifies kidney function into five main categories based on this rate. A consistent eGFR below 60 for three months or more is the threshold used to diagnose CKD. Stage 3 is often the first point where symptoms might appear, split into Stage 3a (45-59) and Stage 3b (30-44). Function below 30 milliliters per minute indicates advanced kidney disease (Stages 4 and 5), requiring substantial medical intervention.
Determining if Improvement is Possible
Whether your eGFR score can improve depends entirely on the underlying cause of the reduced kidney function. The reduction may be due to an acute, temporary problem or a long-term, progressive condition. Acute Kidney Injury (AKI) involves a sudden, rapid drop in eGFR, often caused by temporary issues like severe dehydration, infection, or certain medications.
If the cause of AKI is identified and treated quickly, the eGFR frequently returns to its previous baseline level. This recovery occurs because the kidney structures were temporarily stressed rather than permanently damaged. Healthcare providers monitor the eGFR closely following an AKI episode to confirm the degree of recovery.
In contrast, Chronic Kidney Disease (CKD) involves permanent damage to the kidney’s microscopic filtering units over many months or years. This damage is generally irreversible, making a substantial rise in eGFR back to the normal range unlikely. For individuals with CKD, the goal shifts from full improvement to preservation, focusing on slowing the rate of decline.
Lifestyle Strategies for Kidney Health
Targeted lifestyle changes can noticeably preserve kidney function and slow the progression of CKD.
Sodium Management
Careful management of sodium intake directly influences blood pressure and fluid balance. People with CKD or high blood pressure are often advised to limit daily sodium consumption to between 1,500 and 2,000 milligrams. Reducing processed foods is effective since they are typically high in hidden sodium, which stresses the kidneys. Flavoring meals with herbs, spices, and salt-free blends allows for better control over mineral intake.
Hydration and Fluid Intake
Hydration is important, as water helps flush waste products from the blood. However, those with advanced kidney failure may need to limit fluid intake to avoid fluid overload. Guidance from a physician is required regarding appropriate fluid levels.
Protein and Exercise
Dietary protein intake needs careful consideration because the byproducts of protein metabolism must be filtered by the kidneys. For individuals with an eGFR below 60, a daily protein intake of approximately 0.8 grams per kilogram of body weight is recommended to lessen the kidneys’ workload. For advanced CKD (Stages 4 and 5), further restriction to about 0.6 to 0.7 grams per kilogram per day may be advised, monitored by a dietitian to prevent malnutrition. Regular aerobic physical activity, such as walking or running for more than 30 minutes, has also been shown to improve eGFR and decrease blood pressure in non-dialysis CKD patients.
Quitting Tobacco
The cessation of tobacco use is a powerful step, as smoking significantly harms the kidneys through multiple mechanisms. Nicotine raises blood pressure and heart rate, straining the blood vessels within the kidneys. Smoking also causes vasoconstriction, reducing blood flow and damaging the filtering units, thereby accelerating the loss of function. Quitting smoking immediately lowers these risks and helps slow the progression of kidney disease.
Medical Management of Underlying Causes
Preserving eGFR requires diligent clinical management of the primary conditions that drive kidney disease, mainly high blood pressure and diabetes.
Blood Pressure Control
Blood pressure control is paramount, as sustained high pressure physically damages the glomeruli, the tiny filters inside the kidneys. Guidelines generally suggest a systolic blood pressure (SBP) target below 120 mmHg, or often less than 130/80 mmHg in practice.
Protective Medications
Angiotensin-Converting Enzyme (ACE) inhibitors and Angiotensin Receptor Blockers (ARBs) are frequently prescribed for their protective effect on the kidneys. These drugs lower the pressure inside the glomeruli, a process known as renoprotection, and are beneficial for patients with protein in their urine. A small, initial dip in eGFR is common when starting these medications, which is often a sign of intended pressure reduction and long-term kidney protection.
Diabetes Management
For those with diabetes, strict control of blood sugar is fundamental to preventing microvascular damage to the kidneys. The target for hemoglobin A1c (HbA1c), a measure of average blood sugar, is typically around 7.0%, though this goal is individualized. Newer medications, such as SGLT2 inhibitors, are increasingly used as they slow the progression of kidney disease in people with Type 2 diabetes.
Reviewing Nephrotoxic Drugs
Regularly reviewing all medications with a healthcare provider is an important component of management, especially as kidney function changes. Several common medications are considered nephrotoxic, meaning they can directly harm the kidneys and may require dose adjustment or discontinuation. Examples include Nonsteroidal Anti-inflammatory Drugs (NSAIDs) like ibuprofen, certain antibiotics, and contrast dyes used in medical imaging.