Yes. It is normal to find ketones in urine while fasting. During any typical day, the food that we intake contains carbohydrates that get digested into glucose, and this gets absorbed. This glucose provides the energy for our everyday activities. The additional glucose is stored in the liver and muscles. But during a fasting day, since there is no food intake, the glucose stored in the liver and muscles is used to maintain blood glucose levels. But with prolonged fasting, this alone is insufficient, and fat breakdown occurs to supply energy. Ketones are produced as a by-product during fat breakdown. In general, if your glucose levels are normal and you feel fine, these ketone levels are not dangerous. However, if your blood glucose is more than 200 mg/dl or you feel tired, have vomiting, or feel giddy, you should consult your doctor. If you have a fever, dehydration, or any infections, your doctor may give more importance to the ketones in the urine and ask you to abandon fasting.