Abstract: The present invention relates to a method for measuring a concentration of one or more biomarker in blood from a mammal comprising: —providing a kit of parts for sampling blood comprising a lancet and a capillary, a vial comprising an extraction fluid and one or more internal standard, which is a radioisotope of one or more biomarker adapted to assess a quality and a concentration of the one or more biomarker in the blood sample, —distributing the kit of parts to the mammal, —receiving the vial comprising a blood sample inserted into the vial, —analysing the sample to determine the quality of the sample and the concentration of the one or more biomarker in the blood of the mammal by centrifuging the vial and performing a direct analysis of the supernatant.