H−/D−current and emittance scaling is measured in a magnetic multipole negative ion source. The gas in the source is the only difference as no reoptimization of the source is carried out, thus giving a direct comparison of the performance for the two isotopes. It is found that the H−current is greater than the D−current by approximately a factor of 2 under the same discharge conditions. The extracted electron to ion ratio is commensurately higher in deuterium than in hydrogen. Finally, the emittance in deuterium at the higher arc currents is found to be lower than that in hydrogen. Some comments are made on the scaling within the context of the accepted model of negative ion production.