A method for determining a blood glucose level for a patient, the method comprising, in a system for determining the blood glucose level for the patient, - detecting a present sensor signal at a measuring time tm in a present continuous interstitial blood glucose measurement for a patient; - providing measurement data representing the present sensor signal; - providing sensor signal correction data representing, for the patient, a patient-specific signal correction, the sensor signal correction data being determined from a former interstitial blood glucose measurement for the patient and comprising time delay data representing, for the patient, a patient-specific time delay Δt between a blood glucose value measured in a continuous interstitial blood glucose measurement and a blood glucose reference value measured in a capillary blood glucose measurement, the blood glucose value and the blood glucose reference value referring to the same blood glucose level; - determining corrected measurement data representing a corrected present sensor signal by applying the sensor signal correction data to the present sensor signal; and - determining a blood glucose level for the patient from the corrected measurement data; wherein the applying the sensor signal correction data is further comprising - determining blood glucose level data representing a previous blood glucose level of the patient at a previous time tpr=tm-Δt by determining a blood glucose value from the measurement data and assigning the blood glucose value to the previous time tpr; - providing rate of change data representing a rate of change of the blood glucose level of the patient; and - at least one of the following: - providing present blood glucose level data representing a present blood glucose level of the patient at the measuring time tm by determining a present blood glucose value from the blood glucose value at the previous time tpr and the rate of change of the blood glucose level; and - providing future blood glucose level data representing a future blood glucose level of the patient at a future time tf=tm+Δt by determining a future blood glucose value from the blood glucose value at the previous time tpr and the rate of change of the blood glucose level. - detecting a present sensor signal at a measuring time tm in a present continuous interstitial blood glucose measurement for a patient; - providing measurement data representing the present sensor signal; - providing sensor signal correction data representing, for the patient, a patient-specific signal correction, the sensor signal correction data being determined from a former interstitial blood glucose measurement for the patient and comprising time delay data representing, for the patient, a patient-specific time delay Δt between a blood glucose value measured in a continuous interstitial blood glucose measurement and a blood glucose reference value measured in a capillary blood glucose measurement, the blood glucose value and the blood glucose reference value referring to the same blood glucose level; - determining corrected measurement data representing a corrected present sensor signal by applying the sensor signal correction data to the present sensor signal; and - determining a blood glucose level for the patient from the corrected measurement data; wherein the applying the sensor signal correction data is further comprising - determining blood glucose level data representing a previous blood glucose level of the patient at a previous time tpr=tm-Δt by determining a blood glucose value from the measurement data and assigning the blood glucose value to the previous time tpr; - providing rate of change data representing a rate of change of the blood glucose level of the patient; and - at least one of the following: - providing present blood glucose level data representing a present blood glucose level of the patient at the measuring time tm by determining a present blood glucose value from the blood glucose value at the previous time tpr and the rate of change of the blood glucose level; and - providing future blood glucose level data representing a future blood glucose level of the patient at a future time tf=tm+Δt by determining a future blood glucose value from the blood glucose value at the previous time tpr and the rate of change of the blood glucose level. - providing present blood glucose level data representing a present blood glucose level of the patient at the measuring time tm by determining a present blood glucose value from the blood glucose value at the previous time tpr and the rate of change of the blood glucose level; and - providing future blood glucose level data representing a future blood glucose level of the patient at a future time tf=tm+Δt by determining a future blood glucose value from the blood glucose value at the previous time tpr and the rate of change of the blood glucose level.