An exogenous ketone is a supplemental form of ketone bodies that you ingest instead of your liver producing them. The most common exogenous ketone is betahydroxybutyrate (BHB), which is typically sold as BHB salts (bound to minerals like sodium, potassium, calcium, or magnesium) or as ketone esters.
When you consume exogenous ketones, your blood levels of BHB rise quickly, even if you haven’t been fasting or eating a strict ketogenic diet. This provides your cells—especially your brain and muscles—with an alternate fuel source to glucose, mimicking the temporary state of ketosis without fully overhauling your diet.