Ketones sticks measure the ketone acetoacetate in your urine, which is an unused ketone produced by the body (a by-product of the breakdown of fat). We generally have a certain amount of ketone bodies in our blood, but in a balanced diet they’re not detectable. Only after we stop consuming carbohydrates for an extended period of time (e.g. ketogenic diet) the body starts to produce enough ketones which can be detected.
The body could be burning fat, but urine ketone sticks won’t detect it.
The urine ketone sticks are mainly used by people who want to see if their body is in ketosis. Ketosis is a metabolic state in which some of the body's energy supply comes from ketone bodies in the blood, in contrast to a state of glycolysis in which blood glucose provides energy. Reaching a state of ketosis usually requires an extended deprivation from consuming carbs.
Unlike urine ketone sticks, Lumen will tell you if your body is burning fat regardless of if your body started to produce ketone bodies. You will also be able to see the level of carb usage your body is using to produce energy, which can’t be detected by urine ketone sticks.
It’s important to reiterate that Lumen doesn’t measure ketone bodies but does measure if your body is burning fat.