- The normal blood ketone level in humans is low (about 1 mg/dL) and less than 1mg is excreted per 24h, b/c the ketones are normally metabolized as rapidly as they are formed.  However, if the entry of acetyl-CoA into the citric acid cycle is depressed because of normally decreased supply of the products of glucose metabolism, or if the entry does not increase when the supply of acetyl-CoA increases, acetyl-CoA accumulates, the rate of condensation to acetoacetyl-CoA increases, and more acetoacetate is formed in the liver.  The ability of the tissues to oxidize the ketones is soon exceeded, and they accumulate in the bloodstream (ketosis).  Two of the three ketone bodies, acetoacetate and beta-hydroxybutyrate, are anions of the moderately strong acids acetoacetic acid and beta-hydroxybutyric acid.  Many of their protons are buffered, reducing the decline in pH that would otherwise occur.  However, the buffering capacity can be exceeded, and the metabolic acidosis that develops in conditions such as diabetic ketosis can be severe and even fatal.  Three conditions lead to deficient intracellular glucose supplies, and hence to ketoacidosis: starvation; diabetes mellitus; and a high-fat, low-carbohydrate diet.  The acetone odor on the breath of children who have been vomiting is due to the ketosis of starvation.  Parenteral administration of relatively small amounts of glucose abolishes the ketosis, and it is for this reason that carbohydrate is said to be antiketogenic.

Reference:
1. Ganong's Review of Medical Physiology: 23rd Edition.  Kim E. Barrett et al.  McGraw-Hill Publishing. 2010.