Glomerular Filtration Rate (GFR) estimates how effectively the kidneys filter waste products from the blood. This calculation, derived from a blood test measuring creatinine, is adjusted based on a person’s age, sex, and body size. A “mild decrease” in GFR is common, especially with age, and serves as an early signal that closer monitoring is necessary to protect kidney health.
What a Mild Decreased GFR Number Means
The GFR result classifies the stage of kidney function, where a higher number indicates better filtration. A mild decrease typically falls between 60 and 89 mL/min/1.73m². While this range is often categorized as Chronic Kidney Disease (CKD) Stage 2, a CKD diagnosis requires evidence of kidney damage, such as protein in the urine, persisting for three months or more.
If the GFR is between 60 and 89 without other signs of kidney damage, it may reflect the natural, age-related decline in kidney function. If this mildly reduced GFR is accompanied by markers like elevated protein in the urine (albuminuria), it confirms a diagnosis of early-stage kidney disease. A mild decrease is not a sign of immediate kidney failure, but an early indicator that filtration capacity is below optimal levels.
The GFR calculation used in most labs is the estimated GFR (eGFR), which uses a mathematical formula for assessment. Creatinine, the main marker, can be temporarily influenced by factors like intense exercise, a large meat meal, or severe dehydration. Therefore, a single mildly low result often warrants a repeat test within a few weeks to confirm the decline is chronic, not a temporary fluctuation.
Factors That Contribute to a Decline in GFR
A sustained decline in GFR is frequently linked to chronic conditions that damage the microscopic filtering units, called nephrons. Uncontrolled high blood pressure (hypertension) is a leading cause, as the constant force damages the tiny blood vessels within the kidneys. This damage reduces the efficiency of the glomeruli, the specialized capillary networks responsible for filtration.
Diabetes is another major contributor, where high blood sugar levels injure the cells and membranes of the kidney filters. This damage causes the filtering units to become scarred, accelerating the reduction in GFR. While these two chronic diseases are the primary drivers, the natural process of aging also results in a gradual loss of nephrons, contributing to a lower GFR.
Certain medications can also contribute to a decline in GFR, especially when used regularly. Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen, can interfere with blood flow regulation within the kidneys, potentially causing damage. It is important to discuss all over-the-counter and prescription medications with a healthcare provider when a mild decreased GFR has been identified.
Essential Lifestyle Adjustments and Monitoring
The primary goal upon discovering a mild decreased GFR is to implement strategies that prevent further damage and slow the rate of decline. Managing underlying chronic diseases is necessary, requiring strict adherence to blood pressure and blood sugar control. For individuals with high blood pressure, the target is often to keep readings below 140/90 mmHg, or lower if diabetes is present.
Dietary modifications focus on reducing the workload on the kidneys, starting with a reduction in sodium intake, ideally aiming for less than 2,000 milligrams per day. Lowering salt helps control blood pressure and reduces fluid retention, lessening the strain on the kidneys. Adopting a kidney-friendly eating pattern, such as the DASH or Mediterranean diet, which emphasizes fresh fruits, vegetables, and lean protein, is beneficial.
Protein intake should be moderated, as waste products from protein metabolism must be filtered by the kidneys. While adequate protein is necessary, excessive consumption places an unnecessary burden on the filtering units. Maintaining healthy hydration is important, as sufficient water helps the kidneys excrete toxins, but fluid intake should be balanced and requires personalized guidance.
Avoiding nephrotoxic agents protects the remaining kidney function. This includes minimizing or eliminating the use of over-the-counter NSAIDs and certain supplements, unless approved by a physician. Routine monitoring is necessary, typically involving GFR re-checks every 6 to 12 months, along with urine tests for protein or blood.
Understanding When Specialist Care is Needed
While a mild decreased GFR is often managed by a primary care physician, certain findings indicate that a referral to a nephrologist, a kidney specialist, is appropriate. The threshold for specialist consultation is usually when the GFR drops below 60 mL/min/1.73m², placing the individual into CKD Stage 3 or higher. A rapid or unexplained decline in GFR, even if the number remains above 60, also warrants a specialist evaluation.
The persistent presence of significant amounts of protein in the urine (proteinuria or albuminuria) is a strong indicator for referral, regardless of the GFR number. High levels of protein suggest substantial damage to the kidney filters and require specialized treatment to slow progression. Difficulty managing underlying conditions, such as high blood pressure uncontrolled despite multiple medications, is another reason to seek a nephrologist’s expertise.
Specialists can evaluate unusual causes of kidney disease or manage complications such as anemia or bone density issues that arise even in earlier stages of decline. Seeking specialist care early is associated with better outcomes, as it allows for optimal management plans to be put in place before function is severely compromised.