The strong turbulent mixing within the middle atmosphere should prevent a change of the value of the total hydrogen mixing ratio regardless of the transformation of the hydrogen species in one another within the homosphere. Within the heterosphere the corresponding mixing ratio should drastically increase due to the action of molecular diffusion. We show on the basis of a global three-dimensional model of the dynamics and chemistry of the middle atmosphere that the total mixing ratio decreases under certain conditions when an (escape) flux flows through the domain. The effect occurs particularly above and around the mesopause region, reaching a distinct minimum at about 108 km height. Hunten and Strobel <1974> also found a small reduction on the basis of simplified model calculations, but they stated that the total mixing ratio of hydrogen atoms remains nearly the same. The cause of this apparently paradoxical behavior lies in the fact that under the condition of a hydrogen flux just in the domain of transition of predominant turbulent diffusion to predominant molecular diffusion, a strong decomposition of the heavier H2O component into the light hydrogen constituents takes place, and the temperature increases strongly with height above the mesopause. The marked reduction of the total hydrogen mixing ratio within the extended mesopause region is extremely important for all questions concerning the physics and chemistry of this domain.