Understanding the Relationship Between Sodium and Serum Osmolality

The largest component of the serum osmolality equation is sodium, where a low sodium value in a patient results in an expected low measured serum osmolality. If the measured serum osmolality is not low, then it indicates the presence of something else contributing to the elevated osmolality, ruling out conditions like hypertriglyceridemia, hyperproteinemia, myeloma, or other cancers with extra immunoglobulins.