There is a definite relationship between BG and ketones, but it is not always linear (hope that makes sense). I have had relatively high BG (around 6) but my ketones were well above 0.5. But I could also have low BG (say around 4) without being in ketosis. Low BG is not a guarantee of being in ketosis. My cut-off for ketosis from a BG perspective seems to be around the 6.5 - 7.0 mark, once my BG goes to that level, my ketone production stops almost completely. But this is in line with what Prof Lustig explains in "Sugar - the bitter truth". Insulin goes up, ketones come down, fat burning stops. (Again, I have to stress that although it differs from person to person, the carb load in a day is cumulative - for me it is the same with protein. I can manage my BG, but if I cross the "line" my ketosis stops, although my BG may not always shoot up). Sjoe, I have read this again now and I hope this makes sense ? But this is why I would recommend a dual approach to measuring initially - take the guesswork out of until you get to know your body well enough. So either get a Freestyle type meter where you can measure both BG and ketones or get a BG meter and measure your ketones with urine ketostix. I know a lot of people will try to tell you that the ketostix are not always 100% accurate and that is true, but at least you can see if there are ketones present or not. I have yet to hear of someone who has been so effective at burning ketones that they get a high reading on the blood ketone meter and a low or no reading on the stix. Here's an experiment that dietdoctor Andreas Eenfeldt did with his meter vs ketostix and you will see that you can track the two and the relationship with BG. http://www.dietdoctor.com/final-report-two-months-of-strict-lchf-and-ketone-monitoring I am yet to be convinced of the blood type diet, although there are certain elements relating to carbs that make sense. I have not really immersed myself in blood type diets at all, so my answer here is more of a gut reaction than a qualified or educated one. I am A+, but my wife is a relatively scarce AB+, she is MUCH more carb sensitive than I am (please check your blood type guide if that is in line with what they say ?) - yet I have seen this same high carb sensitivity in most of the females that I have worked with on LCHF - it is almost certainly gender related as well. You would do well to follow that advice, though ! edit: corrected link