Acidosis and related complications cause ketones to appear in urine before the bloodstream, states RnCeus.com. Ketonuria is the condition in which elevated levels of ketone bodies display in urine, which can in turn indicate acidosis. Elevated levels of ketones are common in conditions that inhibit the metabolism, such as diabetes.
Pregnant women should undergo ketonuria screening due to the link between ketoacidosis and intrauterine death, states Wikipedia. Pre-surgery patients or those who suffer from acute illness should have screening as well, as these patients are particularly prone to ketonuria. Starvation, fasting, diets low in carbohydrates and anorexia are other conditions that can cause ketonuria. Ketones are a byproduct of fatty acid metabolism when the body is in short supply of glucose.