They are caused from high glucoses. Ketones are a sign that our bodies are not getting enough energy from glucose. If we are not getting enough energy, lactic acid can build up in our tissues and in the blood. Ketones are also an acid; the more ketones in the blood, the more acid in the blood. Too much acid in the blood is VERY dangerous. Always check ketones if your blood glucose is high, or if you are nauseated or vomiting.