The answer is an increase in ketones. High ketones in the blood from diabetes type I causes diabetic ketoacidosis. Due to the insensitivity of cells to insulin (or lack of production of insulin in the body by the pancreas), the cells are unable to take in glucose for metabolisms, hence the body breaks down fatty acids and amino acids for energy. The metabolites of fatty acid metabolism and the deamination of amino acids are ketones (keto acids) that decrease the blood’s pH.