Ketosis as in the Mosby's Medical dictionary is the abnormal accumulation of ketones in the body resulting from a deficiency or inadequacy in the utilization of carbohydrates (which the body stores and converts to sugar).

Ketoacidosis not only occurs when an animal doesn't eat but also occurs when they are not producing insulin.  Insulin gets glycogen into the cells and in the case of diabetes, due to the lack of, or inadequate insulin, glucose cannot enter the cells.    Because of this inability to metabolize carbohydrates, the muscles become starved for glucose needed to provide the energy for work.   When there is a glucose deficiency in the cells, the ketones are used by the tissue for energy so fat catabolism or fat breakdown begins as an alternative form of energy.  Physiologically, diabetes is a form of starvation. The body breaks down fat first and then muscle to feed the cells.

The by-products of this breakdown are very hard on the system.   The ketone bodies which forms is acetoacetic acid which can cause damage to cells.  At the same time the body is producing ketones, it is not using glucose.  The kidneys, through the production of urine, must remove both.  The higher the ketones and unused glucose levels, the more urine must be produced causing excessive work for the kidneys, and the body will become dehydrated.  The liver has to process the leftovers.   If the body is unable to clear the ketones through the kidneys, they build to toxic levels and eventually lead to Ketoacidosis.   This condition alters the blood chemistry and causes mental changes, i.e. irritability.

Acetone is a Ketone which can be eliminated through the lungs. Ketoacidosis animals often have a chemical smell to their breath similar to nail polish remover (some removers contain acetone).

Often in the established diabetic, the onset of Ketoacidosis is in response to an inflammatory or infectious process going on in the body.

Ketoacidosis or DKA  is a life-threatening medical emergency and ketoacidosis animals must be admitted to the hospital and  treated with intravenous fluids and intravenous short acting insulin as well as the correction of electrolyte imbalances and treatment of the underlying cause. 
DKA is not something which is treated in the home environment

If you are urine testing and are at all unsure of the bg level or feel your pet may be high, it would be wise to use the dual strips (glucose & ketones) when urine testing.  The glucose strips are fine for regular monitoring but check from time to time with the dual strips to alert you of possible ketones present.  If you start getting very high Bg readings or very dark results on urine tests you should probably run a test for the presence of ketones.

1.  polyuria (excessive urination)
2.  polydipsia (excessive water consumption)
3. High blood-sugar levels
4.  High levels of ketones in the urine

Next, other symptoms appear:

5. Constantly tired
6. Anorexia, nausea, vomiting (vomiting can be caused by many illnesses, not just Ketoacidosis!)
7. Abdominal pain
8. Panting
9. Fruity odour on breath
10. Confusion
11. Dehydration (sunken eyeball, reduced tissue turgor, dry tongue)
12. Evidence of precipitation illness (MI, Infection)
13. weight loss
14. Irritability