Ketones are small organic compounds that are produced in the liver by your mitochondria. They work in a similar way to glucose helping your body to create the energy necessary for tasks. There are three types of ketone that are produced in your body. They are called: Acetone, Acetoacetic Acid, and Beta Hydroxybutyrate (also known as BHB).
The third ketone on that list (BHB) is not technically a ketone, it has a slightly different structure – but it works in a similar way and is turned into energy in the same way as Acetone and Acetoacetic Acid. Ketones that are created inside the body are known as endogenous ketones.
You can also supplement your diet with exogenous ketones. These are ketones that are produced outside the body, often exogenous ketone supplements are made from BHB which is then converted into energy inside the body.
Raising ketone levels in the blood is the goal of ketogenic diets, and many people do this through restricting carbs to less than 5% of their calories. Doing this releases ketones as there is no glucose available (the process takes anywhere from three days to a week), this process is called ketosis. You can also use exogenous ketones to increase blood ketone levels, which can help you to enter ketosis or maintain it.