Don’t chase ketone and glucose levels, it will drive you crazy.
Dr. Phinney says that he and Prof. Volek started to see benefits when serum β-hydroxybutyrate reaches 0.5 mmol/L, and that a level of 1.0 seems to be even better, but that levels above 1.0 don’t carry any extra benefit. Blood ketone and glucose levels vary throughout the day, so the time of day you measure will affect your readings.
It appears that levels can be higher during the adaptation phase, but the body becomes more efficient at using them, so excreted ketones (in breath and urine) tend to drop. People on these forums often report levels below 0.5, even though they are clearly in ketosis. (If you are not eating carbohydrate and still breathing in and out, you are making ketones, no matter what your metre tells you.) Fasting ketone levels tend to be higher than the range that Phinney and Volek call “nutritional ketosis.”
Some forum members occasionally report levels that make them wonder if they are at risk for ketoacidosis, but diabetic ketoacidosis is not a concern as long as the pancreas is producing insulin.