Abstract: A fluid mixing unit insertable along conveyance and/or distribution lines, particularly for mixing diagnostic or medical fluids or the like along biomedical lines, comprising a body that is internally hollow and is provided with at least one pair of intake ports for introducing two fluids to be mixed, which are associable with respective feeder devices, and a discharge port for discharging the mixture of the two fluids, which is associable with an outflow device, and a duct for the flow and mixing of the two fluids that is formed in the body and is connected to the intake ports and to the discharge port.