Gum disease or kidney failure? How to tell when bad breath is a sign of something sinister

While some experts link 'ammonia breath' to kidney disease, others disagree: “By the time you feel anything, you’re pretty much working on your last little bit of kidney function."

Robin Roberts 8 minute read March 4, 2022
Young man checking his breath with hand.

When your kidneys are slacking off, your body will look for other ways to excrete your bodily wastes, including through the breath. GETTY

If you notice people making a point of standing six feet away from you and it’s not just about pandemic protocols, it could be your breath. You may even have noticed it yourself behind your N95. But if you skipped the onions at lunch and you’re still stinking up the room, chances are it’s your kidneys trying to tell you something.  

According to the Cleveland Clinic, one of the many causes of bad breath, especially “ammonia breath,” could be chronic kidney disease. When they’re doing their job, your kidneys — those two “kidney” bean-shaped organs, each the size of a fist on either side of your spine just below your rib cage — “clean” your blood by removing wastes and excess fluids, including urea, through your urine, according to the Kidney Foundation of Canada. When your kidneys are slacking off, your body will look for other ways to excrete those wastes, including through the breath. When the urea mixes with saliva, it forms ammonia. Hence, “ammonia breath.”  

How important are kidneys, really?

Your kidneys are as important to your overall health as your heart and lungs. In fact, they filter about a half cup of blood every minute. They also make red blood cells and regulate blood pressure. But most of us don’t pay much attention to them — until they fail.  

Surprisingly, one in 10 Canadians has kidney disease, but because there are few, or even no, symptoms in the early stages, and since it can progress slowly, they won’t know it until the damage is done. 

Common symptoms, according to the Mayo Clinic, include nausea, vomiting, loss of appetite, fatigue, urinating more or less, muscle cramps, dry itchy skin and swollen feet and ankles. But Dr. Mike Bevilacqua, a nephrologist and clinical assistant professor at UBC’s Faculty of Medicine, says the most common symptom is… nothing.

“By the time you feel anything, you’re pretty much working on your last little bit of kidney function,” he says. “For most people, you have to lose 80 per cent or more of your kidney function before you even feel anything.” 

As for bad, or “ammonia,” breath, Bevilacqua says that may be “misleading” because it’s very rare.

“Someone with very advanced kidney dysfunction might notice [their breath], but that would be such a minor amount of people,” he says. “[In fact], for 99.9 per cent of people with kidney disease that will not be the case.” 

Then what else could it be? Well, bad breath could be a sign of postnasal drip, respiratory and tonsil infections, sinus problems, diabetes, liver issues, or a blood disorder. Or it could be simply poor oral hygiene that leads to a condition called periodontal, or gum, disease. 

“Bad breath in and of itself may be an indication that there are higher levels of bacteria that may be present in one’s mouth,” says Dr. Michael Goldberg, a Toronto periodontist who divides his time between his private practice at Toronto’s Cumberland Periodontics and as associate professor in the Faculty of Dentistry at the University of Toronto. He’s also head of the Division of Periodontics at Mount Sinai Hospital where his research seeks connections between oral and systemic health. 

“Obviously, if there are higher levels of bacteria in one’s mouth that might have an effect on at least triggering the immune-inflammatory response in the oral cavity that could ultimately trigger periodontal disease,” he says. “But to suggest that because you have bad breath you have [a serious disease] is, I think, a bit of a stretch.” 

Goldberg does acknowledge, however, that many of the risk factors associated with periodontal disease are also associated with the development of kidney disease and cancers.

“We advocate for oral health as part of the overall health of an individual, it’s not separate,” he says. “So it may be reflective of a poor health condition. If you’re not taking care of your mouth, chances are you’re not taking care of other parts of the body.” 

And that includes taking care of those little fist-sized beans. Bevilacqua says we’re born with way more kidney function than we need, which is why it’s perfectly fine to give one away — for example, as an organ donation — and live a totally normal life. 

But two is optimal, so helping them do their job is vital. First, don’t smoke. Second, maintain a healthy diet and weight. Three, exercise. Also, he says, make sure you’re well-hydrated, and minimize your salt intake. 

“You’re never going to meet someone in Canada who’s salt-deficient, because it’s everywhere,” says Bevilacqua. “About 90 per cent of the salt in our diet comes from pre-made, pre-processed or pre-packaged foods. What you add at the table or cooking with a salt shaker is 10 per cent or less. So it’s a good idea to be diligent about what’s in the package and try to find lower salt options.” 

All of the health in the world won’t help if you are high-risk

But all the health in the world won’t stave off kidney disease if you happen to fall into one of the high-risk categories: people with diabetes, high blood pressure, a family history, or of Aboriginal, Asian, South Asian, Pacific Island, African/Caribbean or Hispanic descent. 

“Some of those groups also, unfortunately, have a higher incidence of some of the other risk factors, like diabetes and high blood pressure,” says Bevilacqua. “Some people will say, for example, that Indigenous patients have a lot of kidney disease, but that’s because they have a lot of diabetes. But that is, by no means, the whole story. They just happen to have higher propensity to develop kidney disease regardless.” So if you’re in a group that’s already prone to have kidney disease without any other disease and you get one of the other common conditions, then you have two strikes that are going to make you more likely to have it.” 

Finding out if you have kidney disease will mean a simple blood, urine and/or imaging test, or even a biopsy. Chronic kidney disease has no cure, and late-stage disease, called kidney failure, requires dialysis or transplant. Warding that off means working with your nephrologist to keep your blood sugar and blood pressure under control, avoid taking painkillers, limiting salt and protein intake, and not smoking. 

Frothy pee like egg white may be a sign of kidney disease

And while he reiterates that bad breath is an unlikely sign of kidney disease — “Things are pretty far gone at that point and you need to go to a hospital” — Bevilacqua says one maybe weird sign would be frothy pee. Kidneys that are falling down on the job are letting things through, such as certain proteins, which can cause your urine to be very bubbly or frothy. “Like whipping an egg white,” he says. 

And, if it turns out to be poor oral hygiene that’s progressed to gum disease, you’ll need to see a periodontist. As with kidney disease, the first sign of gum disease is often no sign. Or you could notice pain or sores in your mouth, bleeding while brushing or flossing, swollen, recessed, red or tender gums, loose teeth — or bad breath. 

Goldberg says treatment depends on the severity of the periodontal disease, and could include a series of deep cleanings, scaling and root planing, and all the way up to surgery and/or bone grafts.  

If left untreated, periodontal disease could cause tooth loss or chronic inflammatory conditions.

“It depends on the level of infection,” he says. “People can develop problems [with] oral bacteria, especially patients that have heart valve replacements. So is it out of the realm of possibility that a severe blood-borne infection that initiated from the oral cavity can cause problems elsewhere? No, but I wouldn’t say it’s a common phenomenon. You would have to have other issues going on to have that happen.” 

One area of research he’s involved with and most excited about is in a compound called resveratrol, found in the skin of red wine grapes. “It may have a bit of a protective effect [against periodontal disease],” he says, “so we’ve started using it for its anti-inflammatory and anti-oxidant effects as an adjunct to treatment.” 

And while Goldberg says this information often gets the attention of his patients, he cautions that it’s not a green light to drink red wine. The resveratrol he’s referring to doesn’t come in a liquid form, it’s a capsule. 


The Kidney Foundation of Canada hosts its 10th Kidney Gala on March 5 to raise funds for, and awareness of, kidney disease and organ donation. The event, whose theme is “Superheroes” to honour patients and their support teams, will be a “virtual live telethon” featuring an online silent auction, entertainment, door prizes and more. The livestream link will be sent to ticket holders. For more information, go to the Kidney Gala site. 

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