Oral Rehydration Salts (ORS) for Travelers: How and When to Use Them
How and when to use oral rehydration salts (ORS) while traveling, why they beat plain water, plus a safe DIY recipe and dehydration warning signs.
What Are Oral Rehydration Salts and When Should Travelers Use Them?
Oral rehydration salts (ORS) are a precise mix of salt (sodium), sugar (glucose), and other electrolytes that you dissolve in clean water to replace fluids lost to diarrhea, vomiting, or heavy sweating. They work better than plain water because of a quirk of gut biology: your intestine absorbs sodium and glucose together, and that pairing pulls water across the gut wall far more efficiently than water alone. For travelers, ORS is the single most useful item to pack for traveler's diarrhea, since dehydration (not the infection itself) is what makes most people feel terrible and is what occasionally lands travelers in the hospital. Use ORS whenever you are losing significant fluid: ongoing diarrhea, repeated vomiting, or dehydration from heat and exertion. Sip it steadily rather than gulping it. In my practice, I tell every traveler to throw a few ORS packets in their bag. They are light, cheap, and occasionally a trip-saver. Here is how to use them correctly.
Why Does ORS Work Better Than Plain Water?
The science is elegant. The lining of your small intestine has a transporter called SGLT1 that moves sodium and glucose into your cells together. Water follows. When you drink plain water during heavy diarrhea, you replace some volume but not the sodium you are losing, and absorption is slower. When you drink a properly balanced sodium-and-glucose solution, you switch on that cotransport mechanism and your gut soaks up both salt and water efficiently. This is the same principle that makes ORS one of the most important public health tools in the world for treating diarrheal dehydration.
What Is in WHO/UNICEF Low-Osmolarity ORS?
The global standard is the WHO/UNICEF low-osmolarity formula, adopted after research showed it works better and more safely than the older, more concentrated recipe. The current formulation has a total osmolarity of about 245 mOsm/L, with sodium around 75 mEq/L, potassium around 20 mEq/L, chloride around 65 mEq/L, and glucose around 13.5 g/L. You do not need to memorize those numbers. The point is that commercial ORS packets are formulated to this standard, which is why they outperform improvised mixes and sports drinks.
How Do You Use Oral Rehydration Salts?
- Use safe water. Mix ORS with clean water: sealed bottled water, water that has been boiled and cooled, or water properly disinfected for drinking. Contaminated water defeats the purpose.
- Follow the packet exactly. Dissolve one packet in the volume of water listed on the label (often one liter). Do not make it stronger; too much salt or sugar can worsen things.
- Sip steadily. Take small, frequent sips over the day rather than drinking a lot at once, especially if you are nauseated. Steady sipping is better tolerated and better absorbed.
- Keep going while losses continue. Replace roughly what you are losing. As diarrhea slows and your urine lightens and increases, you can taper off.
- Mix fresh. Prepare a new batch each day and discard leftover solution that has been sitting out.
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Are Sports Drinks a Good Substitute for ORS?
Not really. Sports drinks are designed for athletes sweating during exercise, not for someone losing fluid to diarrhea. They tend to have too much sugar and too little sodium, so they do not match the balance that makes ORS effective, and the extra sugar can even pull more water into the gut and worsen diarrhea. In a pinch a heavily diluted sports drink is better than nothing, but a proper ORS packet is far better. Pack the real thing.
What Is a Safe DIY Emergency ORS Recipe?
If you run out of packets and cannot buy more, you can make an emergency solution. Measure carefully, because the proportions matter:
- 1 liter of clean, safe water (bottled, boiled and cooled, or properly disinfected)
- 6 level teaspoons of sugar
- 1/2 level teaspoon of salt
Stir until fully dissolved and taste it: it should be no saltier than tears. Too much salt can be harmful, especially for children, so when in doubt make it slightly weaker, not stronger. This homemade version is a backup, not a replacement for commercial ORS, which is more precisely balanced and includes potassium.
A Note on Children
Children dehydrate faster than adults and are more sensitive to getting the mix wrong, so commercial ORS packets are strongly preferred for kids. Offer small amounts frequently. If a child is unable to keep fluids down, is markedly less responsive, has sunken eyes, or is not producing wet diapers or urine, treat that as a medical emergency and seek care right away.
What Are the Signs of Dehydration That Need Medical Care?
ORS handles mild to moderate dehydration well. These signs mean you need more than home rehydration:
- Severe or worsening dizziness or fainting
- Very dark urine, or little to no urination
- Racing heart or rapid breathing
- Confusion, extreme sleepiness, or trouble staying awake
- Inability to keep any fluids down because of persistent vomiting
- Dehydration in an infant, an older adult, or anyone with a serious medical condition
If you cannot keep fluids in, you may need intravenous rehydration, and that is a reason to find care promptly.
Talk to a Wandr clinician about your travel health plan.
Frequently Asked Questions
What are oral rehydration salts used for? ORS replaces fluids and electrolytes lost to diarrhea, vomiting, or heavy sweating. It is the first-line treatment for dehydration from traveler's diarrhea.
Why is ORS better than drinking water? Your gut absorbs sodium and glucose together through a cotransport mechanism, and water follows. A balanced ORS solution switches on that process and replaces both salt and water, which plain water cannot do as well.
Can I use a sports drink instead of ORS? Sports drinks have too much sugar and too little sodium for treating diarrheal dehydration, and the extra sugar can worsen diarrhea. A proper ORS packet is far better. Use a heavily diluted sports drink only as a last resort.
What is the homemade ORS recipe? Mix 1 liter of clean, safe water with 6 level teaspoons of sugar and 1/2 level teaspoon of salt. Measure carefully and never make it saltier than recommended. It is a backup for when packets are not available.
How much ORS should I drink? Sip steadily and aim to replace roughly the fluid you are losing. Continue while diarrhea or vomiting persists, and taper as your urine lightens and increases and symptoms improve.
Is ORS safe for children? Yes, but use commercial ORS packets for children rather than a homemade mix, since kids are more sensitive to incorrect proportions. Offer small amounts often and seek care for any signs of significant dehydration.
When should I see a doctor instead of using ORS at home? Seek care for severe dizziness or fainting, very dark or absent urine, confusion, an inability to keep fluids down, or dehydration in an infant, older adult, or medically vulnerable person.
Sources
- WHO, Cholera outbreaks (homemade ORS recipe and use of safe water): https://www.who.int/news-room/questions-and-answers/item/cholera-outbreaks
- Reduced osmolarity oral rehydration solution for treating dehydration (Cochrane review, PMC): https://pmc.ncbi.nlm.nih.gov/articles/PMC6532752/
- Potency of Oral Rehydration Solution and the sodium-glucose cotransport mechanism (PMC): https://pmc.ncbi.nlm.nih.gov/articles/PMC7210290/
- CDC Yellow Book 2024, Travelers' Diarrhea: https://wwwnc.cdc.gov/travel/yellowbook/2024/preparing/travelers-diarrhea
This article is general education and not individualized medical advice; talk to a licensed clinician about your specific situation.
Mark Karam, PA-C is a board-certified Physician Associate with emergency and urgent care experience and co-founder of Wandr Health.