Oral Rehydration Solution (ORS) is designed to reverse dehydration, the most common cause of death associated with severe diarrhea. The World Health Organization (WHO) and UNICEF standardized this treatment, officially endorsing it in 1978 as a global health priority. This simple, low-cost intervention is credited as one of the most important medical advancements of the 20th century for reducing childhood mortality worldwide. The specific composition of ORS allows for the rapid replacement of fluids and salts lost through conditions like diarrhea and vomiting.
The Official WHO Oral Rehydration Solution Formula
The current WHO and UNICEF standard is the reduced-osmolarity ORS, provided in pre-packaged powder form. This modern formulation has a total osmolarity of 245 milliosmoles per liter (mOsm/L), a reduction from the original 311 mOsm/L formula, which proved more effective in clinical trials. The standardized powder contains four primary ingredients: glucose, sodium chloride (table salt), potassium chloride, and trisodium citrate.
When mixed correctly, the solution provides specific concentrations of electrolytes and sugar per liter of water. These concentrations deliver 75 millimoles (mmol) of sodium and 75 mmol of glucose. Potassium chloride helps replace lost potassium, while trisodium citrate corrects the metabolic acidosis that often accompanies severe diarrhea.
To prepare the commercial packet, the entire contents must be dissolved in exactly one liter of clean, safe drinking water. If the water’s purity is questionable, it should be boiled and cooled first. Using too little water makes the solution too concentrated and can worsen dehydration, while too much water dilutes the ingredients. Once mixed, the solution must be used or discarded within 24 hours to prevent bacterial growth.
How Oral Rehydration Therapy Functions
The specific balance of sodium and glucose in the ORS formula activates the sodium-glucose cotransport system within the small intestine. This mechanism remains functional even during severe diarrheal illness. The ORS works because the glucose molecule acts as a transporter.
When glucose is absorbed by the intestinal lining, it simultaneously pulls a sodium ion into the bloodstream. This movement creates an osmotic gradient. Water naturally follows the sodium, drawing fluid from the intestine into the circulatory system, effectively rehydrating the body.
Plain water or most sports drinks cannot achieve rapid rehydration because they lack the precise ratio of sodium and glucose needed to maximize the cotransport mechanism. The measured concentration in ORS ensures maximum absorption without drawing excess water into the intestine, which occurs with overly sugary solutions. ORS can replenish up to 95% of lost fluids.
Practical Guidelines for Administration and Storage
ORS should be administered immediately at the first signs of fluid loss, such as frequent watery stools or vomiting, and is suitable for all ages. The solution must be given slowly to allow absorption and prevent vomiting. For infants and young children, offer a small spoonful or a slow, steady stream from a syringe every one to two minutes.
If vomiting occurs, pause administration for five to ten minutes, then resume at a slower pace. The total amount of ORS needed depends on the individual’s weight and degree of dehydration. A general guideline is to replace the estimated fluid loss after each loose stool or episode of vomiting.
For a child under two years old, give roughly one-quarter to one-half of a large cup (50–100 ml) after each watery stool. Older children and adults should drink as much as they can tolerate, aiming for half to a full large cup (100–200 ml) after each episode. Breastfeeding infants should continue nursing frequently between ORS administrations.
The mixed solution should be stored in a clean, covered container at room temperature or refrigerated. It must be discarded 24 hours after preparation.
Homemade Alternatives and Critical Safety Warnings
When pre-packaged WHO ORS is unavailable, a simple sugar-salt solution can be prepared at home as a temporary measure, but it requires precise measurement. The widely cited recipe involves mixing six level teaspoons of sugar and half a level teaspoon of table salt into one liter of clean water. Using level measurements is important to ensure the correct balance.
Non-standardized solutions, such as fruit juice, soft drinks, or sports beverages, have an incorrect electrolyte balance. These drinks often contain excessive sugar, which can pull water into the intestine and worsen diarrhea, counteracting rehydration. Furthermore, they usually contain insufficient sodium to trigger the cotransport system properly.
The primary safety warning for home preparation is the risk of using too much salt, which can lead to hypernatremia—high sodium levels in the blood that can be fatal, particularly in children. Conversely, too much sugar can cause osmotic diarrhea, worsening fluid loss. If a person, especially a child, shows signs of severe dehydration, such as lethargy, sunken eyes, or an inability to drink, professional medical attention is necessary, as ORS alone may be insufficient.