The kidneys filter the blood, removing waste products and toxins and maintaining the right balance of fluid and minerals. Most people have two kidneys, located at the middle of the back just under the ribs. The fact that we have two kidneys makes many people assume that we need both of them.
Can a person live with one kidney? What happens if you lose one of them, or if you’re born with just one kidney?
You don’t need both kidneys to live. In fact, having two kidneys gives people far more kidney function than they actually need. This extra kidney function serves as “backup,” but isn’t actually necessary to live a healthy life. Having one kidney is enough for a healthy life.
It’s not understood why people are born with two kidneys when only one kidney is actually necessary, but it does provide some spare kidney function in case something damages one or both of your kidneys.
You can survive with one kidney for just as long as you can survive with two kidneys. Studies have shown that both people born with one kidney and those who donate a kidney to someone else have a normal lifespan.
In fact, the single kidney often enlarges and takes on some of the function of the lost or missing kidney. This results in a kidney function of about 75% in people with one kidney (when compared with 100% in young people with two healthy kidneys). This is greater than the 50% that you might expect from having half the number of kidneys.
People who donate one kidney often see their kidney function decrease to 50% right after the surgery, but it generally increases to around 75% over time as the remaining kidney enlarges and takes on additional function.
When you have just one kidney, it becomes more important to be careful about certain things. Although one healthy kidney is enough, you have less “spare” kidney function, and anything that damages your kidney could be dangerous for you. For example, people with one kidney should not engage in high-impact sports like boxing or football, which can damage the remaining kidney through repeated impacts.
Although people with one kidney can drink alcohol in moderation, it’s important to be careful about how much you drink. Alcohol can cause kidney disease over the long term, so if you have one kidney, make sure to keep your consumption within safe limits – no more than one to two drinks per day.
The kidneys and the immune system are connected, and it’s true that people with severe chronic kidney disease or kidney failure are more susceptible to infections. They’re also more likely to suffer from chronic inflammation, which is linked to a variety of diseases, including cancer. In fact, infections are a common cause of death for people on dialysis.
However, when you have just one kidney, you still have the same amount of kidney function as someone in a very early stage of kidney disease would. Severe immune system dysfunction usually doesn’t show up until later in the course of kidney disease, when the kidneys have lost a lot of their function. As long as you protect your remaining one kidney, you shouldn’t have to worry too much about it affecting your immune system. Although there could be a small effect, it’s unlikely to be a big problem for you.
There are people who are born with only one kidney, a condition known as renal agenesis. There are also those who are born with two kidneys, but only one of them functions properly. This is known as renal dysplasia, and it’s the functional equivalent of being born with one kidney.
Patients with moderate to severe chronic kidney disease are at higher risk for severe outcomes from Covid. However, those with one kidney generally don’t fall into this category. There is therefore no reason to believe that having one kidney makes you high risk for Covid. We can’t say for certain that there’s no increase in risk, but it’s expected to be small.
There are many people who need to get used to living with one kidney after cancer surgery, transplant surgery, or another type of procedure. The emotional recovery can be challenging, but it’s rare for a person who donates a kidney to regret their decision. You will need to have your kidney function monitored regularly, and to be careful with your remaining kidney.
For people with 1 kidney, function needs to be monitored regularly. In some cases, going to a medical laboratory to get samples taken for these tests can become a barrier; for example, early in the Covid pandemic, many people were worried about going to a central location like a medical laboratory, in case they got the virus there. Getting testing at home may be a way to get around this issue. You can order home testing kits for kidney function and take your samples yourself in the privacy and safety of your own home, then mail these to the lab. You’ll then get your results online. This may help patients with one kidney to access the testing that they need.
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Coronavirus (Covid-19) guidance for people with chronic kidney disease. Kidney Care UK. https://www.kidneycareuk.org/news-and-campaigns/news/coronavirus-covid-19-guidance-people-kidney-disease/. Accessed 28 June 2022.
Overall immune profile and effect of chronic kidney disease on vaccination schedule. Indian J Nephrol. 2016 Apr; 26(Suppl 1): S2–S4.
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Solitary or Single-functioning Kidney. National Institute of Diabetes and Digestive and Kidney Disorders. https://www.niddk.nih.gov/health-information/kidney-disease/solitary-kidney. Accessed 28 June 2022.
What to expect after donation. National Kidney Foundation. https://kidney.org/transplantation/livingdonors/what-expect-after-donation. Accessed 28 June 2022.