Comparing Breathe and Blood Ketones

The ACEs unit is approximately equal to 10x the blood ketone equivalent. It is important to remember that the 10x correspondence may not be observed for all measurements. The precise blood/breath correspondence depends upon the individual and upon several other factors. For example, blood and breath ketones do not change at the same rate, and this can lead to deviations from the 10x correspondence when comparing blood and breath directly. If you keep these factors in mind, 10x is a good rule of thumb, but not always applicable.

Depending on your background, there are at least two reasons why you would see deviations from the 10:1 ratio noted in our FAQ:

1. If you have been restricting carbs/fasting for many weeks or months, your body becomes more efficient at using ketones. Once your body is well calibrated to using AcAc for energy, it does not have to convert AcAc to BHB as often. Therefore, we have seen that the ratio of AcAc (and therefore acetone) to BHB is higher in keto-adapted individuals than it is in those who are just starting carb restriction.

2. Our clinical trial showed that there is often a delay between changes in BHB and changes in acetone. This is again due to the nuances of the relationships between the 3 ketones. This delay may also be contributing to the ratios that you are seeing.