The present invention provides methods for measuring, detecting, diagnosing, treating, and researching salt sensitivity and related conditions. In particular, the present invention provides methods for measuring, detecting, diagnosing, treating, and researching salt sensitivity through measuring aberrant red blood cell based potassium efflux levels. In addition, the present invention provides methods for treating conditions involving salt sensitivity (e.g., hypertension), preventing the onset of conditions involving salt sensitivity, identifying individuals at risk for developing salt sensitivity and related conditions, identifying new types of treatment for salt sensitivity and related conditions, and evaluating the effectiveness of treatments for conditions involving salt sensitivity (e.g., hypertension).