A microfluidic circuit cartridge having 3-D hydrodynamic focusing. The cartridge may be fabricated with injection-molded or other molded layers providing a 3-D structure. A flow channel on the card may have a sample core flowing in a fluid of a flow channel for analysis. The sample core may be adjustable in position within the channel with one or more jets or channels of fluid being injected into the flow channel. The jets may also adjust the size of the sample core. There may be a hemoglobin measurement mechanism or card with a cuvette.