Ketotic breath describes the characteristic fruity smell of breath laden with ketones. It can occur in any condition associated with ketosis e.g. diabetic ketosis, starvation.
It is a result of the spontaneous decarboxylation of acetoacetate to acetone. The acetone is expired.
The ability to detect this smell is absent is a sizeable proportion of the population - and, by extrapolation, the medical population. It is important for clinicians to establish whether or not they are able to smell ketones.