Ketones are a chemical made by your liver.
People produce ketones when they do not have enough insulin in their body to turn sugar into energy.
When you are “fat adapted” on the keto diet your body has starts using fat as a fuel source for energy, instead of gluclose/sugar.
Fat becomes ketones injected into your bloodstream for your body to use as fuel.
NOTE: If you are diabetic, too many ketones can become life threatening. This is called ketoacidosis. The blood is too acidic and this condition can lead to coma or death.