When you low carb, your body burns fats, which generates ketones. The state is known as Nutritional Ketosis and is perfectly normal. Ketone levels up to 4mmol/l are considered to be standard.
Diabetic KetoAcidosis (DKA) is the problematic form, when your blood ketone levels become too high and your blood consistency changes to become acidic. This is very dangerous and usually accompanied by high blood glucose levels.
As you are on an LCHF diet and assuming your blood glucose levels are normal, there should be nothing to worry about.