Ketones are produced in the body from the metablism of fats. They are not dangrerous unless you have high sugars and no insulin. then I think that the presence of ketones just means you are building up dangerous levels of blood sugars. High blood sugar is toxic. If you eat a low carb diet and have low blood sugars, ketones are not a problem. Diabetic ketoacidosis is not the same as dietary ketosis . the former is dangerous and a case for inpatient hospital treatment.
There are some people who believe that ketones are the body's natural fuels and that they have been superseded by glucose only in the last 10,000 years since farming, made glucose readily available, as it wasn't in hunter/gatherer times. It's certain that the brain can run on ketones.
If you become ill, your sugars may go high and difficult to control. In that case, ketones in the urine will show that things are going wrong.
