What you should know about kidney health after a COVID-19 infection

COVID-19 is a scary virus — partly because it remains relatively new. We’re still learning about what it does to the body.

You may have heard that the disease can put a strain on your lungs and heart. You might have even heard that long COVID is now considered a disability. But you might not be aware that in some cases, the virus can injure your kidneys.

“Kidney damage is a frequently seen feature with acute COVID infection,” says Thomas Gut, DO. He’s the associate chair of medicine at Staten Island University Hospital in New York City. It’s most common in people who have been hospitalized, he says. But the risk extends even to those who didn’t need medical attention.

In some patients, COVID-related kidney damage can progress to kidney disease. And if you don’t know the signs, the condition can be hard to identify — 9 in 10 people with kidney disease don’t know they have it.

Step 1: Don’t panic. In most cases, kidney damage from COVID is temporary, notes Dr. Gut. It generally improves as COVID inflammation passes. Still, you should understand your risk, the signs to watch for and ways to protect your kidneys from future damage.

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The risk of kidney disease after COVID-19

More than 78 million people have now been diagnosed with COVID-19. Based on research from the St. Louis University School of Medicine, an estimated 28% of them could have COVID-related kidney injury or disease.

For the study, researchers examined the medical records of more than 1.7 million healthy and COVID-infected veterans from March 1, 2020, through March 15, 2021. They found that infected patients who didn’t need to be hospitalized were:

• 15% more likely to develop chronic kidney disease
• 30% more likely to develop acute kidney injury
• 215% more likely to develop end-stage kidney disease

For people who were hospitalized for COVID, the odds were far worse. These patients were:

• 7 times more likely to develop chronic kidney disease
• 8 times more likely to develop acute kidney injury
• 13 times more likely to develop end-stage kidney disease

So how does COVID lead to kidney damage? The mechanism isn’t totally clear, says Dr. Gut. But a study published in the medical journal Cell Stem Cell provides a clue. It found that the virus can cause direct damage to kidney cells and create long-lasting scarring.

The good news is that the risk may be dropping, says David Goldfarb, MD. He’s a kidney specialist at NYU Langone Health in New York City. “This may be because we know more about the disease and thus have better treatments,” he says. “Or maybe people in the first wave got a higher dose of the virus. But in this last Omicron surge, while there were many unvaccinated people admitted to our hospital, there were very few reports of kidney damage.”

How to take care of your kidneys after COVID-19

Even without COVID, about a third of Americans are at risk of developing kidney disease, according to the National Kidney Foundation (NKF). Often this is because they have risk factors such as high blood pressure, diabetes, obesity or a family history of kidney disease.

As noted earlier, around 90% of people with kidney disease don’t even know they have it. So if you have had COVID-19 — even if it was a mild case — it’s worth discussing with your doctor if you should get screened for kidney disease.

There are 2 main tests for kidney disease:

• Albumin-to-creatinine ratio (ACR): This is a simple urine test that looks at 2 compounds. One is a normal waste product called creatinine. If your kidneys are working right, it’s normal to find it in urine. The second compound is albumin, a protein that should still be in your blood — not your urine. If it appears in high levels, it’s a sign that your kidneys aren’t working properly. Three bad ACR test results over a 3-month period is a sign that you have kidney disease, according to the NKF.

• Glomerular filtration rate (GFR): This test focuses on creatinine levels in your blood. If the waste product occurs in high levels, your kidneys aren’t filtering the way they should be.

If you do have kidney disease, you can do a few things to help prevent it from progressing, says Dr. Goldfarb:

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Get your blood pressure under control

High blood pressure can damage your kidneys even more, says Dr. Goldfarb. Ways to lower blood pressure include losing weight and taking blood pressure medication. These include angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARB).

Related reading: Why are there so many types of blood pressure medication?

Monitor your cholesterol and blood glucose levels

Cholesterol and blood sugar (glucose) are both often elevated in people with chronic kidney disease, says Dr. Goldfarb.

So work with your doctor to create a plan for keeping both under control. You may need cholesterol-lowering medications such as statins as well as medications to manage Type 2 diabetes.

Eat for kidney health

A 2019 review of 18 studies from researchers in Australia and New Zealand found that people who ate a healthy diet reduced their risk of chronic kidney disease by 30%. They were also 37% less likely to develop albuminuria, an early indicator of kidney damage.

What did the researchers consider healthy? Diets rich in fruits, veggies, legumes, nuts, whole grains, fish and low-fat dairy. Here’s what to eat (and avoid) if you have kidney disease.

Stay active

The more exercise you get, the lower your risk of kidney disease, according to a 2020 study published in the British Journal of Sports Medicine.

Researchers followed almost 200,000 Taiwanese adults without kidney disease for 18 years. They found that those who were the most physically active were 9% less likely to develop kidney disease during that time compared with those who were more sedentary. (Check out our beginner’s guide to weightlifting for health.)

If something with your body is off — be it muscle cramps, a loss of appetite or a lack of energy — you should visit your doctor. And that’s true regardless of whether you’ve had COVID.

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