eGFR

Introduction

As a Nurse Practitioner in Florida specializing in functional medicine, I frequently help patients interpret their kidney labs. The estimated Glomerular Filtration Rate (eGFR) is one of the most important markers we use to gauge how effectively the kidneys filter waste from the blood.

What Is eGFR?

The eGFR estimates your kidneys’ filtering capacity in milliliters per minute (mL/min). It’s calculated using a formula that includes age, sex, and serum creatinine—a waste byproduct generated by muscle metabolism. Since creatinine is cleared almost exclusively by the kidneys, its blood level serves as a reliable proxy for filtration efficiency.

Why eGFR Matters

Healthy kidneys maintain fluid and electrolyte balance, remove toxins, and regulate blood pressure. A reduced eGFR signals diminished kidney function, which can lead to the buildup of waste products, fluid overload, and serious complications if left unaddressed.

eGFR Ranges and Interpretation

Levels below 60 warrant further evaluation, and those under 15 represent critical loss of function.

Clinical Implications of Low eGFR

A persistently low eGFR (<60) indicates chronic kidney disease (CKD). Early stages are often asymptomatic, making routine screening vital—especially for patients with diabetes or hypertension. As CKD progresses, symptoms like fatigue, fluid retention, and electrolyte imbalances emerge, necessitating interventions to slow decline.

Elevated eGFR

Occasionally, an unusually high eGFR appears in lab reports. In most cases, this is not clinically significant but may reflect assay variability. Always correlate with clinical context and other kidney markers before drawing conclusions.

Factors Influencing eGFR Accuracy

Several variables can skew eGFR estimates:

• Age and Muscle Mass: Older adults or those with low muscle mass may have lower creatinine production, leading to overestimated eGFR.
  
• Diet and Hydration: High protein diets and dehydration can transiently raise creatinine, underestimating eGFR.
  
• Medications: Certain medications—such as trimethoprim, cimetidine, and some antibiotics—interfere with creatinine secretion, falsely lowering eGFR.

Drug Associations

Medications That May Lower eGFR

• NSAIDs: May reduce renal blood flow.
  
• Some Antibiotics: Can impair filtration or secretion of creatinine.

Medications That May Raise eGFR

• Drugs Affecting Creatinine Handling: Agents like trimethoprim can increase serum creatinine without true GFR change.

When to Test eGFR

Routine eGFR testing is recommended for individuals with:

• Diabetes
  
• High blood pressure
  
• Family history of kidney disease
  
• Symptoms suggestive of kidney dysfunction (e.g., swelling, changes in urine output)

Early detection allows for lifestyle modifications and treatments that slow disease progression.

Conclusion
Regular eGFR monitoring under the care of a functional medicine practitioner helps detect early kidney impairment and guides personalized interventions. Combining lab insights with dietary adjustments, exercise, and root-cause therapies empowers patients to preserve kidney health. Consider our IV Therapy options to support hydration and renal function.

Further Reading

• Levey, A. S., Coresh, J., Greene, T., Stevens, L. A., Zhang, Y. L., Hendriksen, S., … & Chronic Kidney Disease Epidemiology Collaboration. (2009). A new equation to estimate glomerular filtration rate. Annals of Internal Medicine, 150(9), 604-612.
  https://pubmed.ncbi.nlm.nih.gov/19414839/

• National Kidney Foundation. (2006). K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. American Journal of Kidney Diseases, 39(2 Suppl 1), S1-S266.
  https://www.kidney.org/professionals/guidelines/guidelines_commentaries

• Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. (2013). KDIGO 2012 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney International Supplements, 3(1), 1-150.
  https://kdigo.org/wp-content/uploads/2017/02/KDIGO_2012_CKD_GL.pdf

• Inker, L. A., Schmid, C. H., Tighiouart, H., Eckfeldt, J. H., Feldman, H. I., Greene, T., … & Levey, A. S. (2012). Estimating glomerular filtration rate from serum creatinine and cystatin C. The New England Journal of Medicine, 367(1), 20-29.
  https://pubmed.ncbi.nlm.nih.gov/22762315/