The simple answer is, yes you can, but that all depends on how strict you are willing to be on a ketogenic diet. The effort and time it takes to put yourself in, and stay in, ketosis is extremely challenging. 

Most people can’t manage the compliance issues associated with eating 5% carbs and 70% fat. Exogenous ketones not only form a bridge for those people to be in ketosis faster and more easily, but allows them greater flexibility when it comes to compliance in being able to still maintain ketosis at high carbohydrate levels. Some studies have shown ketosis done through the use of exogenous ketones can sustain as many as 100mg of carbohydrates and still maintain ketosis. Ketone Supplementation with exogenous ketones allows people to reach higher levels of ketosis and thus some of the benefits of higher levels of ketones can be attained.