Our brain, which accounts for about 2 % of our body weight, uses up to 20 % of our total energy requirements. The supply with sufficient energetic substrates to all brain cells, which are very densely packed, in particular in the human brain, is a huge logistic challenge. The most important energy substrate for our brain is glucose, which reaches the brain via the blood circulation. Glucose is not only utilized by nerve cells directly, but to a large extent also taken up by glial cells, which then either store glucose after conversion to glycogen as energy reserve, or transfer it as lactate to nerve cells. Lactate in nerve cells can then be converted to pyruvate, which is efficiently utilized together with oxygen for the formation of chemical energy in form of ATP. The intermediate metabolic product lactate hence plays an important role as energetic substrate, which is exchanged between cells both under aerobic and non-aerobic conditions. Transport of lactate across the cell membrane is carried out in co-transport with protons (H+), which are crucial regulators of various metabolic processes and membrane transporters. In addition, the lactate carriers form a functional network with carbonic anhydrases, enzymes, which not only catalyze the equilibrium between carbon dioxide, hydrogen carbonate (bicarbonate) and protons, but also facilitate lactate transport. In this article, we focus on physiological processes of the energy metabolism in glial cells as well as on the transfer of energetic substrates to nerve cells, processes, which themselves are critically modulated by pH and its regulation in glial cells.