Calculation of the minimum oxygen concentration in the hypolimnion of lakes based on the balance approach was used to estimate the level of production processes corresponding to the emergence of anoxia in the hypolimnion. Data from regular monitoring of the dissolved oxygen regime in 16 lakes and reservoirs of the world were processed to obtain the linear regression relationships of annual primary production values at which anoxia may appear in the hypolimnion of a lake. An inverse linear dependence of the critical primary production on the lake’s shape factor was established and tested using data from independent observations of the oxygen regime in lakes.