Oral rehydration salts: using them correctly, and the dehydration signs that mean hospital

Oral rehydration salts do not treat diarrhoea and do not stop vomiting. They replace the water and salts already lost — and it is dehydration, not the germ itself, that puts people in hospital. Mixed correctly, ORS is safe and cheap; mixed wrongly, especially stronger than the instructions say, it can make things worse. In Vietnam these sachets are widely sold in pharmacies and are usually called by the name Oresol.

Spotting dehydration — even when the person says they are not thirsty

Dehydration usually does not start with feeling thirsty. Here is what you can observe at home:

• Less urine than usual and darker in colour — the earliest sign, the most reliable, and the easiest to track.
• Dry mouth and tongue, cracked lips, thickened saliva.
• Light-headedness or going dark when standing up, a fast heartbeat, feeling wrung out.
• Skin on the back of the hand, pinched up gently and released, goes back slowly.
• In young children: markedly fewer wet nappies, crying without tears, sunken eyes, a sunken soft spot in babies who still have one, much more fretful or much sleepier than usual.
• In older people: confusion, muddled speech, sleeping a lot, a clear loss of strength over a day or two.

Three things commonly get misread. Older people feel thirst less, so "not thirsty" does not mean they have enough fluid. A child sleeping more than usual is easily taken as "getting better", when it may be lethargy from dehydration. And drinking a great deal of plain water can still end in severe dehydration, because plain water does not replace the salts going out in stool and vomit.

What to do straight away: using ORS correctly

According to CDC, oral rehydration solution is the preferred treatment for mild to moderate dehydration from diarrhoea. It works because of a pre-calculated water–salt–sugar ratio, so the most important thing is not how much you drink but mixing it exactly as the instructions printed on the packaging of the sachet you actually have.

• Mix the whole sachet with exactly the volume of clean water stated on the packaging; water that has been boiled and cooled is safest. Stir until fully dissolved, and do not judge the volume by eye.
• Drink in small sips, steadily. For a young child, give a little at a time with a spoon or a feeding syringe — gulping it down while feeling sick usually leads to more vomiting.
• After each episode of diarrhoea or vomiting, give another round. Chilled is easier to drink.
• Keep breastfeeding and keep eating and drinking normally alongside — prolonged fasting does not speed up recovery.
• A made-up solution is only for use that day; throw away what is left and do not keep it overnight.
• Write down the time of the last urine, along with the number of episodes of vomiting and diarrhoea — this is the first thing a doctor will ask.

The two most dangerous mistakes

1. Mixing it stronger than the instructions to make it "work better". Less water makes the salt concentration in the solution too high, which can push blood sodium to a level that causes seizures — young children and older people suffer the worst consequences. Stronger does not rehydrate faster.
2. Using fizzy drinks, energy drinks or sports drinks instead of ORS. These are high in sugar and do not have the right salt balance; the high sugar also pulls more water into the bowel, making diarrhoea worse.

Things you should not do

• Do not split a sachet to mix it bit by bit "to fit the cup" — splitting the sachet is a guaranteed way to get the ratio wrong.
• Do not mix it with milk, broth, mineral water or fruit juice, and do not add sugar, salt or lemon to a solution you have already made up.
• Do not take anti-diarrhoeal medicines or antibiotics on your own "to get better faster". Most cases need no antibiotic, and anti-diarrhoeal medicines can make things worse when there is a high fever or blood in the stool.
• If it is for a young child, choose a product clearly labelled as suitable for children and follow that product's own instructions; do not convert doses from an adult product yourself.
• Do not drink ORS as an everyday beverage when there is no diarrhoea, vomiting or dehydration.

When to stop rehydrating at home

An intravenous drip is not a better default option: the oral route is safer and enough for most cases. It is for when the oral route is no longer working, and it is a medical procedure requiring a doctor to examine the patient and prescribe it in person.

If you are not sure how dehydrated your relative has become, or you have been giving fluids and they are still not improving, GreenCare nurses and doctors can come to your home, examine them, take vital signs and decide whether a prescribed drip is needed.

This article passes on the recommendations of a public health authority — source: the US CDC — and does not replace being examined in person. Citing CDC here does not imply that CDC endorses Y Te Xanh or our services.

Need personalised advice for your loved one? Call our hotline 094 368 81 15 (24/7) — calling to ask a question or to book costs nothing. GreenCare has doctors who come to examine, nurses who carry out doctor's orders (injections, infusions, dressing changes), remote consultation by video call, and a review of the medicines you are taking; an in-depth remote consultation, or any one after the first, is a paid service. For children we take examination and acute care only — not long-term care at home, and not newborns or expectant mothers. We confirm we have staff in your area and provide transparent pricing before we begin.