If you are a diabetic (usually type I insulin dependent) and your blood sugar is 250+ for 3 days or more <i>and</i> you show the presence of ketones in your urine then you are in ketoacidosis.
Ketoacidosis is a dangerous medical condition resulting in too much acid in the blood.
<i>Ketosis</i>, on the other hand, is a healthy condition and to be desired if you are trying to lose weight.
All ketosis means is that your body is using your own fat as fuel. The ketones are the by products of that process.
Atkins is a ketogenic diet and that means that your body uses the fat you eat and the fat you have stored on your body for fuel.
As a comparison, Weight Watchers is a glucogenic diet. That means that everyone following WW uses glucose from the carbohydrates that they eat as fuel. That process is called glucosis.
Ketosis=very good
Ketoacidosis=very bad