Firstly you can’t get Diabetic ketoacidosis (DKA) unless your body is producing little or no insulin, hence most people with Type2 are NEVER at risk of DKA however high their BG is. (But they may have Type1 even if they have been told they have Type2, one very good reason why insulin levels should be measured in everyone, but the NHS does not do so.)
DKA happens when the insulin level is very low so that cells are not able to take in energy from glucose or ketenes, the body keeps making ketenes but the cells can’t use them. The risk is increased by dehydration, so drink water.
When you are “burning fat” a normal body create a little insulin that lets the cells use ketenes, but not enough insulin to let the cells use glucose.
If you are taking SGLT2 inhibitors (Forxiga, Dapagliflozin, Invokana, Canagliflozin, Jardiance, Empagliflozin, and maybe other brand names) then you can get DKA at low BG levels and if there are any symptoms of DKA you must go to A&E to get a blood gas test regardless of your BG level. (This is one of the reasons that SGLT2 inhibitors are not licensed for Type1 at present.)
Otherwise, your BG must have been over 10 for some time or over about 20 to have a real risk of DKA.
So high BG plus high ketenes => Ring NHS 111