Consumption of salt (NaCl) and potassium (K) has been completely modified, switching from a rich-K/low-NaCl diet in the hunter-gatherer population to the opposite in the modern, westernized population. The ability to conserve K is crucial to maintain the plasma K concentration in a physiological range when dietary K intake is decreased. Moreover, a chronic reduction in the K intake is correlated with an increased blood pressure, an effect worsened by a high-Na diet. The renal adaptation to a low-K diet in order to maintain the plasma K level in the normal range is complex and interconnected with the mechanisms of the Na balance. In this short review, we will recapitulate the general mechanisms allowing the plasma K value to remain in the normal range, when there is a necessity to retain K (response to low-K diet and adaptation to gestation), by focusing on the processes occurring in the most distal part of the nephron. We will particularly outline the mechanisms of K reabsorption and discuss the consequences of its absence on the Na transport systems and the regulation of the extracellular compartment volume and blood pressure.