The present invention provides a systematic approach that allows health care providers (e.g., physicians) to use erythrocyte potassium measurements as an indicator of hypertension or risk of developing hypertension. In particular, the present invention provides systems and methods for treating conditions involving aberrant erythrocyte potassium levels (e.g., hypertension), preventing the onset of conditions involving aberrant erythrocyte potassium levels, identifying individuals at risk for developing hypertension, and evaluating the effectiveness of treatments for conditions involving aberrant erythrocyte potassium levels (e.g., hypertension).