1. Bad Breath
People often report bad breath once they reach full ketosis.
It’s actually a common side effect. Many people on ketogenic diets and similar diets, such as the Atkins diet, report that their breath takes on a fruity smell.
This is caused by elevated ketone levels. The specific culprit is acetone, a ketone that exits the body in your urine and breath (4).
While this breath may be less than ideal for your social life, it can be a positive sign for your diet. Many ketogenic dieters brush their teeth several times per day, or use sugar-free gum to solve the issue.
If you’re using gum or other alternatives like sugar-free drinks, check the label for carbs. These may raise your blood sugar levels and reduce ketone levels.
The bad breath usually goes away after some time on the diet. It is not a permanent thing.
Bottom Line: The ketone acetone is partly expelled via your breath, which can cause bad or fruity-smelling breath on a ketogenic diet.