The analysis of materials including or implanted with hydrogen by means of an ion beam often causes depletion of the hydrogen content. This phenomenon, commonly observed during ERD analyses, is particularly pronounced with polymers or polymer-like materials. Direct measurement of the original hydrogen profile of the quantitative determination of hydrogen is therefore very difficult. However, measurements of the total quantity of hydrogen as a function of the total analysing fluence can be made and, in principle, can be extrapolated to zero fluence, i.e. to the original quantity of hydrogen. For that purpose, it is common practice to use multiple-term inverse exponential curves to fit the experimental data. This practice is however inadequate and the results obtained are of questionable rigor and meaning. We have deduced a mathematically more elegant and physically more plausible function for the fitting based on the generalized exponential integral function which has a minimum number of parameters and which seems to be applicable to all common hydrogen depletion curves. The small number of parameters in the equation and their coherence indicate a possible link with a physical process. The equation, although empirical, could therefore be useful for the comparison of different depletion curves and it may even give some insights for the development of a quantitative, physical model.