What are the advantages of measuring ketones in blood compared to urine

Accuracy
The concentration of ketone bodies in the blood reflects the current state of metabolism. The urine ketone value measures acetoacetate, a degradation product of ketones that is excreted in urine. The measurement is semi-quantitative and less sensitive than the measurement of BHB in the blood. This value may be less accurate as it depends on hydration and kidney efficiency.

Temporal precision
An efficient monitoring of current ketone levels can only be achieved via the blood. The urine ketone level reflects a delayed state.

Reliability in long-term ketosis
Ketone levels in urine may be less accurate during prolonged ketosis, as the body uses ketones more efficiently over time and excretes less of them in the urine.