The machines that I have encountered flash Ketones? when the BM is above 20 (IIRC). The guidelines state that DKA should be considered if the BM is consistently above 11 mmol/l AND ketones in urine 3+ OR ketones in blood >0.6 mmol/l. The NHS choices website says that DKA is unlikely with blood ketones between 0.6 and 1.5; between 1.6 and 2.9 there is an increased risk of DKA, above 3 is a medical emergency (999 ambulance). With elevated ketones you feel absolute rubbish and you look unwell, vomiting profusely. A person with type 1 is twice as likely to develop DKA as a person with type 2 ( I can't remember the reference). If your BM is above 35 and you're type 2 then you're in a hyperglycaemic, hyperosmolar state (HHS aka HONK), and again is a medical emergency, although some BM machines only show Hi above 30 or 35 and not the value depending on the individual manufacturer.