Causes of trace amounts of ketones in a urinalysis include early stages of ketoacidosis in diabetics, fasting, starvation, a low-carbohydrate or high-protein diet, and severe illness, states MedlinePlus. Other causes are fever, burns, hyperthyroidism, pregnancy and lactation. Anorexia nervosa, vomiting and increased metabolism are additional causes.
When the body does not get enough carbohydrates or sugar, it breaks down fats and fatty acids for fuel, which produces ketones, states MedlinePlus. Ketones in trace amounts can indicate the body is beginning to build up stores, according to Healthline. A patient who has self-tested for ketones needs to retest several hours later to determine whether the level has increased. If so, the patient needs to see a doctor.