WHO sodium target (ORS)

The WHO sodium target (ORS) refers to the concentration of sodium in the oral rehydration solution adopted by the World Health Organization and UNICEF.

Background and formulation

Oral rehydration therapy replaces fluids and electrolytes lost during diarrheal illness. Early formulations contained around 90 mmol/L of sodium, but this concentration sometimes led to hypernatremia. In 2003 WHO and UNICEF revised the formula to a reduced‑osmolarity solution containing 75 mmol/L of sodium and 75 mmol/L of glucose. The reduced sodium level maintains effective water uptake by the intestines via the sodium–glucose co‑transport mechanism while lowering the risk of excessive sodium retention. Along with 20 mmol/L of potassium, 65 mmol/L of chloride and 10 mmol/L of citrate, this composition has been shown to decrease stool output and vomiting and reduce the need for intravenous fluids. The WHO sodium target has become the global standard for treating dehydration caused by cholera and childhood diarrhea and is used in millions of rehydration sachets distributed around the world.

Implications for sports hydration

Athletes lose sodium through sweat, but the concentration is usually lower than that found in diarrhea. Sweat sodium concentrations typically range from about 20 to 60 mmol/L, depending on genetics, heat acclimation and diet. When mixing homemade sports drinks or oral rehydration solutions for use during prolonged exercise, using a sodium concentration similar to the WHO target can help support fluid absorption without causing gastric discomfort. Paired with modest amounts of glucose, sodium facilitates water transport across the intestinal wall. However, athletes should adjust the sodium content to match their personal sweat rate and salt loss; those with very salty sweat may benefit from higher concentrations. As with any rehydration strategy, testing during training is important.

Understanding the WHO sodium target helps athletes and coaches gauge how much sodium to include in a rehydration solution and highlights the balance needed between electrolyte replacement and palatability.

Related Terms: Reduced‑osmolarity ORS, Glucose–sodium co‑transport, Trisodium citrate (ORS), Dilution ratio, Custom blend