The renal solute load (RSL) is the sum of the materials that must be excreted via the urine, including urea, sodium, potassium, and chloride.

Each gram of protein ingested yields a RSL of 5.8 mOsm in adults and 4.0 mOsm in children. Protein yields a lower RSL in growing children and those in anabolic states since more dietary protein is being used to synthesize body proteins. On the other hand, the RSL will be higher in catabolic patients.

Each mEq of electrolyte yields a RSL of 1 mOsm.