Ketoacidosis is a type of metabolic acidosis which is caused by high concentrations of keto acids, formed by the deamination of amino acids. This is most common in untreated Type 1 diabetes, when the liver breaks down proteins in response to a perceived need for respiratory substrate.

The acidity results from the dissociation of the H⁺ ion at physiological pH of metabolic Ketone Bodies such as Acetoacetate, and B-hydroxybutyrate , produced from ketogenesis.

Further Reading

The Merck Manual -

Diabetic Ketoacidosis http://www.merck.com/mrkshared/mmanual/section2/chapter13/13b.jsp

Alcoholic Ketoacidosis http://www.merck.com/mrkshared/mmanual/section2/chapter13/13c.jsp