Device for aliquoting and filtering blood, comprising: an element (1, 10) for collecting blood (S); a capillary conduit (2) which has a capillary force greater than that of said collecting element and is in fluid communication therewith; and a dispensing element (3) which has a capillary force greater than that of the capillary conduit and is in fluid communication therewith; characterized in that said dispensing element comprises a filtering device (3) for separating blood cells from plasma.