Sodium

Sodium is the main electrolyte of the fluid outside the cells, regulating water balance, blood volume, osmotic pressure and nerve transmission, working in tandem with chloride. An adequate supply is essential, and severe deficiency, though rare with a complete food, can cause fatigue and disturbances of fluid balance. Perception of sodium in pet food is heavily coloured by human nutrition, and that import causes confusion. Contrary to a widespread belief, a moderately raised sodium level is not a marker of poor quality. In fact, urinary-health diets sometimes use a controlled, higher sodium content on purpose, to encourage drinking and increase urine volume, which dilutes the minerals that form stones and lowers the risk (peer-reviewed veterinary literature). The opposite move also has its place: in animals with advanced heart disease or certain kidney diseases, sodium restriction may be advised to limit fluid retention. Both adjustments belong to a veterinary strategy rather than a blanket rule that less is always better. Dietary sources include added salt, meat and fish. Formulation aims for an intake matched to the life stage and health goal, balanced against [potassium](/glossary/potassium) and chloride. On a label, sodium and chloride appear among the analytical constituents on more detailed packs. See the [Petipedia glossary](/glossary).

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