COVID-19 can damage the kidneys during the acute illness and accelerate kidney function decline for months or years afterward. Acute kidney injury develops in a substantial fraction of hospitalized COVID patients, and emerging data show that kidney filtration rates drop faster in the years following infection than would be expected from aging alone. The mechanisms are varied, the risks are not evenly distributed, and recovery depends heavily on how sick you were in the first place.
How the Virus Reaches the Kidneys
SARS-CoV-2 enters cells by latching onto a protein called ACE2, with an assist from another protein called TMPRSS2. The lungs get the most attention because that is where the virus causes the most obvious harm, but the kidneys express high levels of both ACE2 and TMPRSS2, making them a natural secondary target.1PubMed Central. Covid-19 and kidney injury: Pathophysiology and molecular mechanisms Post-mortem studies have found viral particles inside both the tubular lining of the kidney and specialized cells called podocytes, which help filter blood.2Nature Reviews Nephrology. COVID-19-associated acute kidney injury: consensus report of the 25th Acute Disease Quality Initiative (ADQI) Workgroup
Direct viral invasion is only one piece of it. The immune overreaction sometimes called a “cytokine storm” can damage kidney tissue from the inside out. On top of that, the virus triggers problems with blood clotting and inflammation in small blood vessels throughout the body, which hits the kidneys hard because they are essentially dense networks of tiny blood vessels. Complement activation and microclotting within the kidney have been identified as distinct mechanisms of injury, separate from both direct infection and immune overreaction.2Nature Reviews Nephrology. COVID-19-associated acute kidney injury: consensus report of the 25th Acute Disease Quality Initiative (ADQI) Workgroup So the damage is not a single event but a pileup of insults from several directions at once.3PubMed Central. COVID-19 associated acute kidney injury
Acute Kidney Injury During Hospitalization
Among people sick enough to be hospitalized with COVID, kidney injury is common. A large study of over 5,400 patients admitted to hospitals in the New York area found that about 37% developed acute kidney injury, and roughly 14% of those needed dialysis or a similar form of kidney replacement therapy. The connection to respiratory failure was stark: nearly 90% of patients on mechanical ventilation developed some degree of kidney injury, compared to about 22% of those who were not ventilated.4PubMed Central. Acute kidney injury in patients hospitalized with COVID-19 The sicker the lungs, in other words, the worse the kidneys tended to fare.
Risk factors for developing kidney injury during a COVID hospitalization line up with the conditions you would expect: older age, diabetes, high blood pressure, cardiovascular disease, and the need for blood pressure support medications in the ICU.4PubMed Central. Acute kidney injury in patients hospitalized with COVID-19 Black patients were also at higher risk, a finding that connects to a genetic vulnerability discussed later in this article.
How COVID Compares to Influenza
One question researchers asked early was whether COVID’s kidney effects were simply what happens when any severe respiratory infection hits. The answer appears to be no. A comparison of hospitalized U.S. veterans with COVID versus those with influenza found that kidney injury occurred in about 41% of COVID patients compared to roughly 29% with the flu. COVID-related kidney injury was also more severe, and blood or protein in the urine was more common. Among patients who survived, the rate of kidney recovery was similar between the two groups, suggesting that the excess damage from COVID is driven by the higher likelihood of getting injured in the first place, not by a fundamentally different recovery process.5PubMed Central. Comparison of COVID-19 versus influenza on the incidence, features, and recovery from acute kidney injury in hospitalized United States Veterans
A separate study comparing patients who had kidney injury from COVID with those who had kidney injury from influenza or other illnesses found something perhaps counterintuitive: the COVID group actually had lower rates of worsened kidney function and lower all-cause mortality over follow-up than the group with kidney injury from other causes. This may reflect the different age profiles and baseline health of the populations, but it complicates any simple narrative that COVID is uniquely destructive to kidneys in the long run.6JAMA Internal Medicine. COVID-19−Associated Acute Kidney Injury and Longitudinal Kidney Outcomes
Long-Term Kidney Function Decline
The more pressing question for most people is what happens to the kidneys months and years after a COVID infection has cleared. Two large studies paint a broadly consistent picture. A study following patients in post-COVID recovery clinics in British Columbia found that kidney filtration rates dropped by roughly 3% in the first year after infection, with the decline being steepest in those who were hospitalized (about 7%) and those with diabetes (about 6%).7Nephrology Dialysis Transplantation. Long-term effect of COVID-19 infection on kidney function among COVID-19 patients followed in post-COVID-19 recovery clinics in British Columbia, Canada More than 40% of patients in that study were at risk of developing chronic kidney disease.
A second study put those numbers in perspective by comparing COVID patients to people who had been hospitalized with pneumonia. After adjustments, the COVID group’s kidney function declined about 1 mL/min/1.73 m² faster per year than the pneumonia group overall. Among those who had been hospitalized, the gap widened to about 2.6 mL/min/1.73 m² per year faster.8JAMA Network Open. Kidney Function Decline After COVID-19 Infection To put that in plain terms, normal aging costs you roughly 1 mL/min/1.73 m² of filtration per year after age 40. A hospitalized COVID infection roughly triples that pace of decline, at least in the years immediately following.
A scoping review of the broader literature on what researchers have begun calling “renal long COVID” concluded that chronic kidney disease development and progression may follow COVID infection, and that acute kidney injury during the initial illness appears to be a key driver.9PubMed Central. Renal Long COVID: A Scoping Review Whether this accelerated decline eventually levels off or continues at the same pace remains an open question that longer follow-up data will need to answer.
Who Faces the Greatest Risk
People With Pre-Existing Kidney Disease
If you already have chronic kidney disease, COVID is disproportionately dangerous. A nationwide analysis found that the odds of dying from COVID in the hospital climbed steadily with each stage of kidney disease, from about 34% higher in stage 3 to more than two and a half times higher in stage 5.10Frontiers in Medicine. Nationwide in-hospital mortality and morbidity analysis of COVID-19 in advanced chronic kidney disease, dialysis and kidney transplant recipients A study of ICU patients found that about half of those on dialysis or with chronic kidney disease who were admitted to intensive care died within 28 days, compared to about 35% without pre-existing kidney disease.11PubMed Central. Characteristics and Outcomes of Individuals With Pre-existing Kidney Disease and COVID-19 Admitted to Intensive Care Units in the United States
Beyond survival, the trajectory of kidney function worsens too. A study of CKD patients in the Bronx found that those who were hospitalized with COVID experienced kidney function decline of about 2.1 mL/min/1.73 m² per year, compared to about 1.1 mL/min/1.73 m² per year in CKD patients who were not infected. Even non-hospitalized COVID patients with CKD faced higher risks of major adverse kidney events at 6, 12, and 24 months.12Scientific Reports. Long term outcomes of patients with chronic kidney disease after COVID-19 in an urban population in the Bronx
Kidney Transplant Recipients
People living with a transplanted kidney face a double bind: their immune-suppressing medications make them more susceptible to severe COVID, and COVID itself threatens the transplanted organ. An early case series of ten transplant recipients found that 50% developed acute kidney injury and 30% died.13PubMed Central. COVID-19 in kidney transplant recipients A multicenter study of transplant recipients with COVID-related kidney injury found that only about 41% achieved complete recovery of graft function at three months. Graft failure occurred in about 14% of patients, and biopsies revealed a range of damage including tubular injury and microclotting.14PubMed Central. Recovery of kidney function after AKI because of COVID-19 in kidney transplant recipients
There is a more encouraging note from the vaccine era. A large study comparing outcomes before and after COVID vaccines became available found that among transplant recipients who survived three months after infection, rates of graft rejection and graft loss at two years were similar in both eras, but mortality dropped from about 6% to about 5%.15American Journal of Transplantation. Impact of COVID-19 Infection and Vaccination on Long-Term Graft Function in Kidney Transplant Recipients The improvement is modest but meaningful for a population that has consistently been among the most vulnerable.
A Genetic Factor in Certain Populations
A pattern noticed early in the pandemic was the appearance of a specific form of kidney damage, collapsing glomerulopathy, in Black patients with COVID. This condition involves a dramatic collapse of the filtering units of the kidney and is linked to variants of a gene called APOL1. A case series found that all six patients presenting with this form of kidney damage had the high-risk APOL1 genotype.16PubMed Central. AKI and Collapsing Glomerulopathy Associated with COVID-19 and APOL 1 High-Risk Genotype A similar pattern was seen in additional case reports, and the condition resembles HIV-associated kidney disease, though it remains unclear whether the underlying mechanism is the same.17Kidney Medicine. Molecular Analysis of the Kidney From a Patient With COVID-19–Associated Collapsing Glomerulopathy APOL1 risk alleles are carried by a significant fraction of people of West African descent, making this a population-specific vulnerability worth knowing about.
Children and Kidney Involvement
Children generally tolerate COVID far better than adults, but kidney injury is not unheard of, particularly in a condition called multisystem inflammatory syndrome in children (MIS-C). A study of 152 children hospitalized with either acute COVID or MIS-C found that about 12% developed kidney injury overall, but the rate was dramatically higher in children with MIS-C: 54% compared to 11% with straightforward acute COVID.18Frontiers in Pediatrics. Acute Kidney Injury in Pediatric Acute SARS-CoV-2 Infection and Multisystem Inflammatory Syndrome in Children (MIS-C): Is There a Difference? The good news from that study was that all children recovered kidney function and none needed dialysis.
A meta-analysis looking specifically at MIS-C estimated that about 20% of children with MIS-C develop kidney injury, and about 15% of those need kidney replacement therapy. The odds of dying were nearly five times higher in children with kidney injury compared to those without it.19PubMed Central. Acute kidney injury following multisystem inflammatory syndrome associated with SARS-CoV-2 infection in children: a systematic review and meta-analysis So while pediatric cases are less common and often recover well, kidney involvement when it does occur is a warning sign of a more severe course.
Recovery Prospects for Severe Cases
Among the most critically ill COVID patients who needed dialysis in the ICU, outcomes were grim but not universally so. A multicenter study of 876 ICU patients who required dialysis during COVID found that 67% died, 11% had persistent kidney failure at discharge, and 22% had recovered enough kidney function to stop dialysis before leaving the hospital.20PubMed Central. Kidney Recovery and Death in Critically Ill Patients With COVID-19-Associated Acute Kidney Injury Treated With Dialysis: The STOP-COVID Cohort Study A smaller Italian study reported that among patients who survived 90 days, about a third required ongoing dialysis, about a third had incomplete recovery, and a third recovered kidney function fully.21PubMed Central. Long-term outcome of COVID-19 patients with acute kidney injury requiring kidney replacement therapy
Among survivors overall, the picture is brighter. A study tracking patients who needed acute dialysis during COVID found that among those who survived, about 83% showed evidence of kidney recovery by the end of follow-up, though median kidney function at that point still sat around 61 mL/min/1.73 m², which is below normal.22PLOS ONE. High rate of renal recovery in survivors of COVID-19 associated acute renal failure requiring renal replacement therapy Recovery, in other words, often means improved but not restored to where you started.
Vaccination Cuts Kidney Risk Substantially
One of the clearest practical takeaways from the research is that vaccination dramatically lowers the risk of COVID-related kidney injury. A large cohort study found that the 30-day risk of kidney injury after COVID vaccination was about 0.66%, compared to 4.88% after COVID infection. After adjusting for demographics and existing health conditions, infection carried about ten times the risk of kidney injury compared to vaccination.23npj Vaccines. Assessing acute kidney injury risk after COVID vaccination and infection in a large cohort study That is a wide enough gap that it applies even to people worried about vaccine side effects on the kidneys: the infection itself is far more dangerous to your kidneys than the vaccine.
Early Detection and What Doctors Watch For
Standard kidney monitoring relies on measuring creatinine in the blood, which is a lagging indicator since it does not rise until significant damage has already occurred. Researchers have been investigating whether newer biomarkers could catch COVID-related kidney injury earlier. One promising candidate is KIM-1 (kidney injury molecule-1), a protein released by damaged tubular cells. In COVID patients, KIM-1 levels were significantly higher in those who went on to develop kidney injury and in those who needed ICU admission.24Journal of Nephrology. Kidney injury molecule-1: potential biomarker of acute kidney injury and disease severity in patients with COVID-19 It performed well as a predictor, though it has not yet become part of routine clinical practice.
There is also an unresolved debate in pathology about how to confirm direct viral infection of the kidneys. While detecting viral RNA in kidney tissue produces consistent results, using electron microscopy to visualize actual virus particles has proven unreliable because certain normal cellular structures can mimic the appearance of viral particles, leading to potential false positives.25PubMed Central. COVID-19 effects on the kidney This matters because the question of how often the virus directly infects the kidney versus how often the kidney is collateral damage from immune overreaction has practical implications for treatment strategies.
The Broader Burden on Kidney Care
The individual-level data adds up to a public health problem. Modeling work from the UK projected that the pandemic-era acceleration in chronic kidney disease progression could push advanced CKD costs substantially higher by the mid-2030s, potentially exceeding what healthcare systems are prepared to deliver.26LSHTM Research Online. Long-term kidney outcomes after COVID-19 The concern is not just cost but capacity: dialysis slots, transplant infrastructure, and nephrology staffing were already under pressure before COVID, and an influx of patients with accelerated kidney decline could overwhelm existing resources.
Chronic kidney disease already imposes enormous health and economic costs through dialysis, lost employment, and premature death.27PubMed Central. Impact of COVID-19 on the worsening crisis of chronic kidney disease: the imperative to fund early detection is now If COVID has indeed shifted a large number of people a few years closer to needing dialysis than they otherwise would have been, the downstream effects on healthcare systems will be playing out for a decade or more. The consensus from the nephrology community is that long-term kidney monitoring after COVID recovery, especially for anyone who was hospitalized or who had documented kidney injury during infection, is worth the investment in catching problems early.9PubMed Central. Renal Long COVID: A Scoping Review
What About the Renin-Angiotensin System and Long COVID
Because SARS-CoV-2 hijacks ACE2, a key player in the body’s blood-pressure regulation system, there was early speculation that long-lasting disruption to that system might explain some of the persistent symptoms grouped under “long COVID,” including ongoing kidney effects. A study of healthcare workers tested this by measuring four markers of the renin-angiotensin system at 3 to 6 months and again at 12 months after infection. No significant differences were found between people with long COVID symptoms and those without.28PubMed Central. Is long-term disruption of the renin-angiotensin-aldosterone system associated with long COVID? A retrospective cohort study among healthcare workers The study was small enough that a subtle effect could have been missed, but it does push back against the straightforward version of the theory that the virus permanently throws the blood-pressure regulation system out of balance. Whatever is driving the longer-term kidney effects, the mechanism is likely more complex than a single disrupted hormone pathway.