💧 Oral Rehydration Therapy: How to Make It and When to Use It

One of the most consequential medical breakthroughs of the twentieth century required no laboratory equipment, no pharmaceutical supply chain, and no trained clinician to deliver. Oral rehydration therapy — ORT — is a sugar-salt-water solution mixed in a specific ratio that allows the body to absorb fluids even when illness has disrupted normal fluid balance. The World Health Organization estimates it has saved the lives of more than 70 million children since it entered widespread use in the 1970s. Most of those deaths were prevented not in hospitals, but in homes, villages, and refugee camps, by caregivers working from memory or a printed card.

The simplicity of oral rehydration therapy is also its most misunderstood feature. A small error in the ratio — more salt, more sugar, or the wrong volume of water — produces something that may either fail to work or actively worsen dehydration. The mechanics are precise even if the ingredients are not exotic. Understanding why the formula is what it is turns a piece of advice into something a person can apply correctly under pressure, without a label to read or a pharmacist to ask.

This article covers the oral rehydration therapy formula, how to make it and when to use it, the biology that explains why it works, the situations where it is not enough, and the common substitutes that fall short of therapeutic standards.

🌍 Why Oral Rehydration Therapy Matters Beyond the Clinic

Before ORT, dehydration from diarrhoeal disease was treated primarily with intravenous fluids — a hospital-dependent intervention that was unavailable to most of the world’s population and logistically impossible during disease outbreaks affecting thousands simultaneously. The discovery that glucose and sodium are absorbed together across the intestinal wall — even during active diarrhoea — meant that fluids could be delivered orally with near-equivalent effectiveness in the majority of cases.

This is not a minor refinement of medical practice. Diarrhoeal disease remains the second leading cause of death in children under five globally. In emergency settings — displacement, flooding, conflict, infrastructure collapse — it spreads rapidly and can kill a previously healthy child within hours if dehydration is not corrected. ORT transforms a hospital-dependent treatment into a household intervention that requires only two common ingredients and clean water.

For preparedness purposes, the implications are direct. In any extended emergency that disrupts healthcare access, increases waterborne disease risk, or places people under physical stress, dehydration becomes a real threat — not just for children, but for adults weakened by illness, heat, or insufficient fluid intake. Knowing how to make and administer ORT correctly is a genuinely life-relevant skill.

🔬 Why the Formula Works: Glucose-Sodium Co-Transport

The intestinal wall normally absorbs sodium through a mechanism that is partially disabled during diarrhoea. However, a separate transport channel exists that absorbs glucose and sodium simultaneously — and this channel remains functional even during acute illness. When glucose is present in the right concentration alongside sodium, it acts as a molecular co-transporter, pulling sodium — and therefore water — across the intestinal wall and into the bloodstream.

This is why the ratio of sugar to salt is not arbitrary. Too much glucose overwhelms the transport mechanism and creates an osmotic gradient that draws water into the intestinal lumen rather than out of it — worsening diarrhoea. Too little glucose, and the co-transport mechanism doesn’t activate efficiently. Too much salt without enough fluid volume, and you add a sodium load the kidneys must process, which in a dehydrated person is a burden their body cannot easily manage.

The WHO formula threads this needle with precision: a glucose concentration low enough to avoid osmotic problems, a sodium concentration that matches physiological requirements, and a fluid volume that allows gradual restoration of circulating blood volume.

Understanding this mechanism matters practically. It explains why you cannot substitute freely with sweet drinks, why the water volume is part of the formula, and why the measurement precision you would bring to any other medical procedure should be brought here too.

🥄 The WHO Oral Rehydration Solution Formula

The standard WHO ORS formula for home preparation is:

Ingredient	Metric	Imperial (approximate)
Clean water	1 litre (1,000 ml)	4 cups / 34 fl oz
Sugar (white, granulated)	6 level teaspoons	2 level tablespoons
Salt (plain table salt, non-iodised preferred)	½ level teaspoon	½ level teaspoon

Yield: 1 litre of ORS, approximately 6 adult doses or sufficient for a small child over 4–6 hours.

Preparation Steps

Begin with clean water. If your water supply is compromised, boil it first and allow it to cool to room temperature before mixing. Adding ingredients to hot water is acceptable, but give to the patient once cooled — hot fluid is harder to consume in the necessary volumes.
Measure the sugar precisely. Use a standard 5 ml teaspoon, levelled flat with the back of a knife. Do not use a heaped teaspoon. Six level teaspoons of granulated white sugar is the target. Brown sugar can be used if white is unavailable — the slightly higher molasses content makes no meaningful difference at these concentrations.
Measure the salt precisely. Half a level teaspoon. This is the measurement most commonly approximated incorrectly — a heaped half-teaspoon contains significantly more sodium than the formula intends. If in doubt, err toward slightly less rather than more.
Stir thoroughly until both ingredients have fully dissolved. Undissolved salt or sugar sitting at the bottom of the container means the patient is receiving an uneven concentration.
Taste before administering. The finished solution should taste roughly as salty as tears — not strongly salty, not sweet. If it tastes significantly saltier than tears, discard and remix. A noticeably salty solution means too much salt was used.
Label and time the container. ORS prepared at room temperature should be used within 24 hours. Discard any unused portion after this point — do not store and reheat.

💡 Tip: Pre-measure your salt and sugar into clearly labelled small containers before an emergency. Having a pre-portioned packet ready removes the risk of measuring errors when you are tired, stressed, or working in poor light.

🛒 Gear Pick: For any preparedness kit, pre-formulated WHO-standard ORS sachets — such as Dioralyte (UK/Europe) or Pedialyte powder packets (North America) — remove all measurement uncertainty. Each sachet dissolves in exactly the stated volume of water and delivers the correct electrolyte profile. Store a 20–30 sachet supply alongside your water reserves.

⚗️ Variations and Substitutions: What Works and What Does Not

Can you add flavour?

A small amount of fruit juice can be added to improve palatability, particularly for children who resist drinking an unflavoured solution. This is a reasonable concession to get fluid into a sick person who would otherwise refuse. A splash — 50–100 ml (2–3 fl oz) per litre — does not meaningfully alter the electrolyte balance. More than this begins to dilute the sodium and increase the sugar concentration beyond the therapeutic window.

Rice water ORS

In parts of Asia and South Asia, a traditional variant uses water from cooked rice in place of plain water. This has been studied and found effective — the glucose polymers in rice starch are broken down by intestinal enzymes and provide a slower, more sustained glucose release than refined sugar. If white rice is available and you have the fuel and water to cook it, rice water ORS is a viable alternative. The formula: cook 50 g (about ¼ cup) of white rice in 1 litre of water until soft, strain off the water, cool, and add the same ½ teaspoon of salt. No additional sugar is needed.

What about sports drinks?

This question comes up frequently and deserves a direct answer. Gatorade, Powerade, and equivalent sports drinks are formulated for a fundamentally different purpose — maintaining performance in athletes who are sweating, not rehydrating people who are losing fluid through illness. The differences matter:

	WHO ORS	Typical Sports Drink
Sodium	~75 mmol/L	~10–20 mmol/L
Glucose	~75 mmol/L	~50–80 mmol/L (higher in many)
Osmolarity	~245 mOsm/L	~280–390 mOsm/L
Therapeutic purpose	Clinical rehydration	Performance maintenance

The sodium content in sports drinks is too low to drive effective co-transport. The sugar content in many formulations is too high, and the osmolarity in some exceeds that of blood, which creates an osmotic gradient that can worsen diarrhoeal losses. In mild dehydration where ORS is not available and no illness is driving fluid loss, a sports drink is better than nothing. As a clinical replacement for ORS in a sick child with diarrhoea, it falls short and can sometimes make things worse.

The same applies to cola, fruit juice, and sweetened teas — all too high in sugar, all too low in sodium for therapeutic use.

📌 Note: Coconut water has gained a reputation as a natural ORS equivalent. It has some validity — fresh coconut water contains meaningful potassium and some sodium, and its osmolarity is close to that of ORS. However, its sodium content is lower than the WHO formula and its glucose concentration varies. In a scenario where ORS sachets and basic ingredients are genuinely unavailable, coconut water is a reasonable emergency option for mild dehydration. It is not a clinical equivalent.

🏥 When to Use ORT: Appropriate Indications

Oral rehydration therapy is appropriate for mild to moderate dehydration caused by:

Acute diarrhoea (viral or bacterial gastroenteritis)
Vomiting that has partially resolved and is allowing some oral intake
Heat-related dehydration without neurological symptoms
Inadequate fluid intake during fever or illness
Physical exertion in hot conditions combined with insufficient drinking

The signs of dehydration you should recognise before they become dangerous are your clinical guide to whether ORT is the right intervention. Mild to moderate dehydration — dry mouth, reduced urine output, lethargy, skin tenting that resolves within a second or two — responds well to oral therapy. These cases represent the majority of dehydration episodes across all settings.

Dosing and administration

Adults and children over 10: Sip 200–400 ml (7–14 fl oz) of ORS per hour for the first few hours, then continue at a lower rate as the patient improves. The goal is not to drink a large volume quickly — it is to keep pace with ongoing losses while gradually restoring the deficit.

Children aged 2–10: 100–200 ml (3–7 fl oz) per hour, adjusted downward if vomiting is occurring. Give small amounts frequently — a teaspoon every minute or two — rather than trying to administer a larger volume at once. A child who vomits immediately after a large mouthful loses most of the dose; a child who receives small, frequent sips tends to retain more even when nauseated.

Children under 2: Follow medical guidance where available. In an emergency, small frequent sips — a few millilitres at a time — applied patiently. Continue breastfeeding alongside ORS if the child is breastfed.

Concurrent with ongoing losses: For every loose stool, give an additional 50–100 ml (2–3 fl oz) of ORS in a small child; 100–200 ml (3–7 fl oz) in an adult. ORT is not a one-time dose — it must keep pace with what the body continues to lose.

🚨 When ORT Is Not Enough: Escalation Indicators

This is the most important section of this article. Oral rehydration therapy is highly effective within its appropriate range. Used in situations beyond that range, it can give a false sense that treatment is occurring while the patient’s condition worsens.

Escalate beyond ORT immediately if any of the following are present:

Altered consciousness, confusion, or inability to respond normally — severe dehydration affecting brain perfusion; requires intravenous fluids
The patient cannot swallow or maintain oral intake due to unconsciousness, persistent vomiting, or refusal
Persistent vomiting within minutes of every attempt to drink — oral route is compromised; IV access is required
Sunken eyes with no improvement, very dry mouth and tongue, and no urine output for 8+ hours — severe dehydration in an adult; more urgent in a child
Fontanelle (soft spot) sunken in a young infant — severe dehydration in a baby; this is a medical emergency
Signs of shock: rapid weak pulse, cold clammy extremities, pale or grey skin, very rapid breathing
Blood in stool combined with high fever — suggests bacterial dysentery that may require antibiotic treatment, not ORT alone
Symptoms of cholera-like illness: profuse, watery “rice water” stools in large volumes with rapid deterioration — ORT can partially help but IV rehydration is usually required
A child under 2 who has had six or more watery stools in 24 hours and is worsening despite oral therapy

When these indicators are present and medical care is available, the priority is transport. When medical care is not accessible — a scenario that is exactly the situation preparedness planning must address — the focus shifts to maintaining airway, positioning the patient to prevent aspiration if unconscious, and attempting to maintain any oral intake that is possible.

The article Diarrhoea and Dehydration: The Most Dangerous Combination in a Crisis covers the escalation decision in greater clinical depth, including the assessment tools available without equipment.

📋 Quick Reference: ORT Decision Flow

Person appears dehydrated (dry mouth, reduced urine, lethargy)?
        │
        ▼
Can they swallow and keep fluid down?
    │                   │
   YES                  NO
    │                   │
    ▼                   ▼
Any danger signs?    → Severe dehydration or unconscious?
(see :::danger above)   → EVACUATE / seek IV care
    │
    ├── YES → ESCALATE. ORT alone is not sufficient.
    │
    └── NO  → BEGIN ORT
              │
              ├── Adult: 200–400 ml/hr, sipped slowly
              ├── Child 2–10: 100–200 ml/hr, small frequent sips
              └── Under 2: small sips every 1–2 min + continue breastfeeding
                          │
                          ▼
              Reassess every 2 hours:
              Improving (urinating, more alert, moist mouth)?
                  │                    │
                 YES                   NO
                  │                    │
              Continue ORT         Reassess for
              until resolved       escalation signs

⚖️ ORT in Adults vs Children: Different Risks, Same Principles

Adults have a larger fluid reserve relative to their body mass than children, and the rate at which dehydration becomes life-threatening is correspondingly slower. A healthy adult can tolerate moderate dehydration for longer before organ function is compromised. This is not a reason to be relaxed about adult dehydration — it means the window for effective oral therapy is wider, not that the problem is less serious.

Children are at dramatically higher risk precisely because the volume of fluid loss represents a larger proportion of their circulating blood volume. A toddler with gastroenteritis who passes six watery stools in four hours may have lost a clinically significant fraction of their blood volume in that time. ORT works well in children — it was developed primarily with paediatric populations in mind — but the timeline is compressed and reassessment must be more frequent.

The elderly present a specific additional risk: diminished thirst sensation means they may not recognise or report thirst reliably, reduced kidney reserve means electrolyte imbalances develop more quickly, and some medications (diuretics, ACE inhibitors) alter fluid and electrolyte handling in ways that complicate both dehydration and rehydration. For older adults on regular medications, the threshold for escalation should be lower and the supervision of ORT more attentive. The electrolyte considerations for this group are covered further in Electrolyte Balance During Water Rationing: What You Need to Know.

🔁 How Long to Continue ORT

ORT continues until the patient has been rehydrated and ongoing losses have stopped or slowed to a level the body can manage through normal dietary intake. Recovery indicators:

Return of normal urine output (pale yellow, not dark amber or absent)
Moist mouth and tongue
Improved alertness and responsiveness
Reduced frequency and volume of diarrhoeal stools
The patient feels thirsty and is drinking voluntarily

Once these indicators are present and stable, transition to normal fluid and food intake. Reintroduce food gradually — bland, easily digested foods such as rice, bread, bananas, and boiled potato. The old advice to withhold food entirely during diarrhoeal illness is outdated; early reintroduction of food speeds intestinal recovery.

Continue offering ORS alongside normal food and fluids for 12–24 hours after apparent recovery, particularly in children and elderly patients.

❓ Frequently Asked Questions

Q: What is oral rehydration therapy and when should you use it? A: Oral rehydration therapy is a specific sugar-salt-water solution that restores fluid and electrolyte balance in people with mild to moderate dehydration, most commonly caused by diarrhoea, vomiting, heat, or illness. Use it when someone shows signs of dehydration — dry mouth, reduced urine, lethargy — and is still able to swallow and retain fluids. It is not a substitute for intravenous treatment in severe dehydration.

Q: How do you make oral rehydration solution at home with basic ingredients? A: The WHO home preparation formula is 1 litre (4 cups) of clean water, 6 level teaspoons of white sugar, and ½ level teaspoon of plain salt. Stir until both dissolve fully. The solution should taste faintly salty — roughly like tears. Use within 24 hours and discard unused portions. Measurement precision matters; a heaped teaspoon of salt rather than a level one can produce a solution with excess sodium.

Q: What is the WHO formula for oral rehydration salts? A: The standard WHO ORS formula targets approximately 75 mmol/L of both sodium and glucose, with an osmolarity of around 245 mOsm/L. The home version — 1 litre of water, 6 level teaspoons sugar, ½ teaspoon salt — approximates this. Pre-packaged WHO-formula sachets (Dioralyte, Pedialyte powder, and equivalents) are more precise and are worth including in any preparedness supply.

Q: When is oral rehydration therapy not enough and medical help is needed? A: ORT is not sufficient when the patient is unconscious or cannot swallow, when vomiting prevents any oral intake, when there are signs of shock (rapid weak pulse, cold skin, confusion), when a young infant has a sunken fontanelle, or when there has been no urine output for eight or more hours. These signs indicate severe dehydration requiring intravenous fluids. If medical care is unavailable, focus on keeping the airway clear and attempt any oral intake the patient can tolerate.

Q: Can you use sports drinks like Gatorade instead of ORS? A: Not as a clinical replacement. Sports drinks have sodium levels roughly four to seven times lower than WHO ORS and glucose concentrations that are often too high for therapeutic rehydration. In mild dehydration without illness, a sports drink is better than plain water — but in illness-driven dehydration, particularly diarrhoea, sports drinks do not drive the glucose-sodium co-transport mechanism efficiently and some formulations may worsen fluid losses. Use a properly made ORS or pre-packaged sachets where possible.

💭 Final Thoughts

There is something worth sitting with in the fact that one of the most effective medical interventions ever developed costs almost nothing, requires no training beyond reading a formula, and has been available for over fifty years — yet remains unknown to the majority of people who might one day need it.

ORT does not require a pharmacy, a clinic, or a stable grid. It requires sugar, salt, clean water, and the knowledge that the ratio matters. That last part — understanding enough of the mechanism to measure carefully and recognise when the approach is insufficient — is the difference between having a skill and having a half-remembered piece of advice.

In a crisis where illness spreads through compromised water, heat dehydrates faster than people drink, or medical care is hours away rather than minutes, ORT is not a backup plan. It is likely to be the primary clinical intervention available. Treat learning it with the seriousness that deserves.

© 2026 The Prepared Zone. All rights reserved. Original article: https://www.thepreparedzone.com/water-hydration/hydration-and-water-rationing/oral-rehydration-therapy-how-to-make-it-and-when-to-use-it/