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What Is the Relationship between Ketosis and Breath?

By Marlene Garcia
Updated May 17, 2024
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Ketosis and breath that turns foul are side effects of a low carbohydrate diet, and might occur in diabetics when the pancreas cannot create enough insulin. Breath might smell sweet or fruity when restricting carbohydrates because of changes in metabolism. Ketosis and breath concerns stem from the presence of ketones, chemical molecules that produce acetone, defined as a waste product excreted through the lungs and urine.

Ketones regulate the body’s pH balance and metabolism. These chemicals aid digestion of nutrients from food and store excess carbohydrates as fat. When a diet restricts carbohydrates, ketones are released by the liver to begin converting fat and protein into energy. This process is called ketosis, and breath is affected as acetone leaves the lungs through respiration.

Another relationship between ketosis and breath might stem from the body using more water when metabolism changes. A person might become dehydrated, causing less saliva to form in the mouth. Without sufficient saliva, levels of bacteria might increase, leading to bad breath.

Ketosis and breath odor typically resolve within a few weeks after fasting or starting a low-carbohydrate diet. Some dieters use breath mints or sugarless gum to mask the unpleasant odor. Increasing fluid intake might help, along with chewing on sprigs of fresh parsley. The condition is not linked to dental hygiene, but to an overabundance of acetone in the lungs.

Diabetics might experience ketosis and breath odors when not enough insulin is produced by the pancreas. This hormone allows cells to absorb glucose, a simple sugar obtained via carbohydrates, to use as energy. If glucose cannot be absorbed, it remains in the blood, causing the body to release ketones to convert protein and fat into energy. Prolonged ketosis in diabetic patients could lead to coma and death from excessive ketones in the blood.

Ketosis can be tested through urine strips that turn purple when ketones are present. This typically indicates the body is using fat for energy. Some dieters experience headaches or dizziness along with ketosis and breath problems at the onset of dieting. Fatigue and insomnia might also occur. The level of ketosis and bad breath depends upon how severely the diet restricts carbohydrates.

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Discussion Comments

By bear78 — On Sep 14, 2014

I'm suspecting that I might be in ketosis due to my diet as well. I'm going to purchase a ketone test strip kit tonight and test my ketone levels. Thankfully, these test strips are available at pharmacies.

My dietitian said that this will resolve on its own fairly soon. But I still want to know what my ketone levels are like. If they are high, I don't think I will continue with this diet. I'm not worried about foul breath. I just don't want to put my health at risk.

By literally45 — On Sep 13, 2014

@SarahGen-- I'm not a diabetic but this happened to me once when I was on a low carbohydrate diet. I'm sure that my ketone levels were not as high as a diabetic's. But they must have been high because I noticed the changed in the scent of my breath. I agree with you that the ketones cause a strange mouth odor.

By SarahGen — On Sep 13, 2014

Ketones don't just make the breath of a diabetic smell fruity, they can also make a diabetic's sweat smell fruity. But it's not a good fruity smell. Sometimes it smells like alcohol, other times, it smells like spoiled fruit, sweet but foul. It's a strange odor but it's the tell tale sign of diabetes.

Since the body uses fat for energy, the ketones that are produces accumulate in the body and are released through urine, sweat and breath. Anyone who experiences this symptom needs to see their doctor right away.

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