Recently, while at a conference on integrative approaches to kidney disease, I realized how wide the information gap remains between nephrology and the other providers who care for patients with kidney conditions. One area where this gap is particularly evident is in dialysis and its impact on patients’ lives. At the Integrative Kidney Institute, much of our work focuses on pre-dialysis CKD management and prevention. But what about those already on dialysis? This blog aims to initiate a conversation about dialysis patients, helping to bridge the gap in understanding. One of the most common questions I hear is: “How much kidney function does dialysis really replace compared to normal kidneys?” The answer underscores both the life-saving role of dialysis and its essential limitations.
By Majd Isreb, MD, FACP, FASN, IFMCP
How Much Kidney Function Does Dialysis Really Replace?
Normal Kidney Function: The Gold Standard
Healthy kidneys are remarkable organs, working around the clock, not just for hours at a time, but continuously, 24 hours a day, 7 days a week. Each kidney contains about one million microscopic filters called nephrons, and together they produce a glomerular filtration rate (GFR) of about 100–120 mL/min. This means that in a single day, the kidneys filter 150–180 liters of plasma, carefully selecting what to keep and what to eliminate.
But filtration is only part of the story. After blood is filtered, the kidneys perform the fine-tuned work of reabsorption and secretion. They reclaim essential substances such as glucose, amino acids, and bicarbonate, while discarding excess waste products like urea and creatinine.
Kidneys are also master regulators:
-
Electrolyte balance: They maintain stable levels of sodium, potassium, calcium, phosphate, and magnesium, all of which are vital for heart, nerve, and muscle function.
-
Fluid balance: By adjusting urine concentration, kidneys ensure that the body doesn’t dehydrate or become overloaded with fluid.
-
Blood pressure regulation: Through the renin–angiotensin–aldosterone system, kidneys help keep blood pressure within a healthy range.
-
Hormonal functions: They produce erythropoietin, which stimulates red blood cell production in the bone marrow, and they activate vitamin D, which is essential for calcium absorption and bone health.
Taken together, these functions highlight why healthy kidneys are irreplaceable. Dialysis can replicate some of the waste and fluid removal, but it cannot fully substitute for the round-the-clock, multi-layered work of normal kidneys.
In-Center Hemodialysis: The Standard Approach
Most patients in the U.S. receive in-center hemodialysis three times a week, for 3–5 hours per session. When averaged over time, this provides the equivalent of about 10–15 mL/min of GFR—roughly 10–15% of normal kidney clearance.
Because dialysis is intermittent, toxins and fluid build up between treatments and are then rapidly removed during the session. This “sawtooth” pattern stresses the cardiovascular system and leads to inflammation, never fully matching the smooth regulation of healthy kidneys.
Peritoneal Dialysis: More Continuous Control
Peritoneal dialysis (PD), done daily either manually or with a nighttime machine, provides a similar clearance rate—around 10–15 mL/min equivalent GFR, which also reflects 10-15% of normal kidney clearance. The difference is that PD runs every day, so the body experiences fewer fluctuations. While it may not deliver higher clearance overall, it offers steadier toxin and fluid removal, which many patients find more tolerable.
Home Hemodialysis: Closing the Gap
Advances in home-based therapies enable more frequent and prolonged treatments, which more closely mimic natural kidney function.
-
Short Daily HD (5–7 times per week): Delivers around 20–25 mL/min equivalent GFR, roughly doubling the clearance of in-center dialysis.
-
Nocturnal HD (6–7 nights per week, 6–8 hours per session): Can achieve 40–60 mL/min equivalent GFR, approaching 50–60% of normal kidney function. This more continuous therapy is associated with smoother fluid balance, better blood pressure control, and improved outcomes.
The Bottom Line
Even at its best, dialysis cannot fully replicate the function of healthy kidneys. Beyond clearance, it does not replace the hormonal and metabolic roles kidneys play. That’s why transplantation remains the closest thing to normal kidney health.
Still, understanding how different dialysis options compare helps patients and providers choose the best therapy for each individual’s needs and lifestyle.
