You should test your blood or urine for ketones whenever:
• There is an unexplained rise in your blood sugar, or you have a blood sugar level of more than 250 mg/dl (13.9 mmol/l) for two tests in a row;
• You have symptoms of nausea, vomiting, confusion, or severe fatigue;
• You have any symptoms of ketoacidosis such as increased thirst and urination, stomachache, or dry mouth;
• If you have a flu, infection, or injury;
• When you’re planning to exercise, but your blood sugar is over 250 mg/dl.
• If you are pregnant, check for ketones each morning before breakfast or whenever your glucose goes over 250 mg/dl.
Learn more about ketones here.