What does a low Glomerular Filtration Rate (GFR) mean?

Understanding Low Glomerular Filtration Rate (GFR)

A low GFR indicates reduced kidney function, which can range from mild kidney damage to severe kidney failure requiring dialysis or transplantation. The severity and implications depend on how low your GFR is and whether you have other signs of kidney damage 1.

What GFR Measures

GFR measures how well your kidneys filter blood. It's calculated from your serum creatinine level and other factors like age, gender, and race. Normal GFR values are:

• ≥90 mL/min/1.73 m²: Normal kidney function (Stage 1 if kidney damage is present)
• 60-89 mL/min/1.73 m²: Mildly decreased function (Stage 2 if kidney damage is present)
• 45-59 mL/min/1.73 m²: Mild to moderate decrease (Stage 3a)
• 30-44 mL/min/1.73 m²: Moderate to severe decrease (Stage 3b)
• 15-29 mL/min/1.73 m²: Severe decrease (Stage 4)
• <15 mL/min/1.73 m²: Kidney failure (Stage 5) 1, 2

Clinical Significance of Low GFR

Kidney Function

• Indicates reduced ability to filter waste products from blood
• May signal chronic kidney disease (CKD) if present for >3 months
• Affects medication clearance, requiring dose adjustments for many drugs

Associated Complications

As GFR decreases, the risk of complications increases:

• GFR <60 mL/min/1.73 m²:

  • Increased risk of cardiovascular disease
  • Higher prevalence of hypertension (approaching 80% in advanced CKD) 1
  • Metabolic abnormalities begin to appear

• GFR <30 mL/min/1.73 m²:

  • Anemia becomes more common
  • Mineral and bone disorders develop
  • Metabolic acidosis
  • Multiple abnormalities (hypertension, anemia, hypoalbuminemia) affect about 20% of patients 1

What to Do If Your GFR Is Low

1. Confirm the result:

   • Repeat testing to verify low GFR
   • Check for albuminuria/proteinuria (urine albumin-to-creatinine ratio) 2

2. Determine if it's acute or chronic:

   • Acute: Recent onset (less than 3 months)
   • Chronic: Present for 3+ months 1

3. Medical evaluation:

   • Blood pressure measurement (hypertension is common with low GFR)
   • Blood tests for electrolytes, calcium, phosphorus
   • Complete urinalysis to check for protein, blood, or other abnormalities 1, 2

4. Treatment approaches:

   • Blood pressure control: ACE inhibitors or ARBs are preferred, especially if you have albuminuria 1, 3
   • Lifestyle modifications:
     • Reduce sodium intake to <2 g/day
     • Moderate protein intake (approximately 0.8 g/kg/day) 1, 2
     • Avoid nephrotoxic medications like NSAIDs 2
   • Glucose control if you have diabetes 1

5. Nephrology referral is recommended when:

   • GFR <30 mL/min/1.73 m² (Stage 4-5)
   • Rapid decline in kidney function
   • Significant albuminuria
   • Difficult management issues 2

6. Renal replacement therapy should be considered when:

   • GFR <15 mL/min/1.73 m² with symptoms or complications
   • Severe fluid overload, refractory hyperkalemia, severe acidosis, or uremic symptoms 1, 2

Important Considerations

• Age affects normal GFR values. In adults over 70, values slightly below 60 mL/min/1.73 m² may be physiologically normal 4
• A single low GFR reading doesn't necessarily indicate chronic kidney disease - it must be present for at least 3 months 1
• Acute decreases in GFR >15% are associated with higher risk of adverse kidney outcomes 5
• Regular monitoring of kidney function is essential if you have a low GFR - typically every 3-6 months depending on severity 2

Remember that early detection and management of kidney disease can significantly slow progression and reduce complications. If your GFR is low, work closely with your healthcare provider to develop an appropriate management plan.