In short
Most diarrhoea settles on its own, and the treatment that matters is fluid replacement rather than medicine to stop it. Oral rehydration salts and zinc do the real work, especially in children.
Emergency if: Drowsiness or unresponsiveness, sunken eyes, inability to drink, a skin pinch taking two seconds or more to flatten, or no urine passed for many hours.
On your report
Sodium, Potassium, Bicarbonate (CO2), Creatinine +3 more
On this page
01
What counts as diarrhoea
Diarrhoea is defined as the passage of 3 or more loose or liquid stools per day, or more frequent passage than is normal for the individual. The second half of that definition matters: what is normal varies widely between people, and frequent formed stools are not diarrhoea.
There are three clinical types, and they are managed differently. Acute watery diarrhoea lasts hours to days. Acute bloody diarrhoea, also called dysentery, points to a different set of causes and needs medical assessment. Persistent diarrhoea lasts 14 days or more and always warrants investigation rather than continued self-treatment.
02
Dehydration is what causes harm
The danger in acute diarrhoea is almost never the infection — it is losing water and salts faster than they are replaced. That is why the priority is replacing fluid from the first loose stool rather than waiting to see whether it settles, and why the very young and the very old deteriorate fastest.
Severe dehydration is recognised by at least two of the following: lethargy or unconsciousness, sunken eyes, being unable to drink or drinking poorly, and a skin pinch that goes back very slowly, taking two seconds or more. These signs mean intravenous fluids are needed and are not a situation to manage at home.
03
Oral rehydration salts, made properly
Oral rehydration solution is a mixture of clean water, salt and sugar in a specific ratio, and the ratio is what makes it work: glucose and sodium are absorbed together across the gut wall, dragging water with them even while the gut is inflamed. Plain water does not do this, and is why water alone is not enough in significant diarrhoea.
Use the whole sachet in exactly the stated volume of clean water. Halving the water to make it taste better makes the solution too concentrated and can worsen the diarrhoea, which is the commonest error. Give it in small frequent sips rather than large drinks, offer more after each loose stool, and continue until the stools are formed. Sugary soft drinks and energy drinks are not substitutes.
04
Zinc, and continuing to eat
For children, a 10 to 14 day course of supplemental dispersible zinc tablets reduces the duration of the episode by about 25% and the stool volume by about 30%. The full course is given even after the diarrhoea stops, because part of the benefit is a reduced chance of further episodes over the following months.
Feeding should continue throughout. Breastfeeding carries on as normal and more often, and older children and adults should eat as soon as they are able rather than fasting the gut. Withholding food prolongs recovery. Simple, well-tolerated foods are fine, and there is no need for a restrictive regimen.
05
Medicines that help, and those that do not
Antibiotics are unnecessary in most cases because the majority of episodes are viral, and using them adds side effects and drives resistance without shortening the illness. They are reserved for specific situations identified by a doctor, such as dysentery or particular confirmed infections.
Anti-motility medicines that slow the bowel can give adults short-term relief for practical reasons, but they do not treat the cause. They should not be used in children, and should be avoided by anyone with bloody stools or a high fever, because slowing the gut in those situations can make matters considerably worse.
06
When to seek help
Get medical advice for blood in the stool, a high fever, persistent vomiting that prevents fluids staying down, severe abdominal pain, signs of dehydration, or diarrhoea lasting more than a few days in an adult or more than a day or two in a small child. Recent antibiotic use, recent travel, or a weakened immune system all lower the threshold for getting checked.
Prevention deserves as much attention as treatment. Handwashing with soap at the key moments, safe drinking water, careful food handling, and rotavirus vaccination for infants prevent far more illness than any treatment resolves. Anyone with diarrhoea should stay away from work, school or food handling until 48 hours after the last episode.
When to act
Routine — see a doctor
Watery diarrhoea for a day or two in a well adult: oral rehydration solution after each loose stool, normal eating, and no antibiotics.
Same-day — call promptly
Blood in the stool, high fever, diarrhoea lasting more than a few days, recent antibiotics, or any diarrhoea in an infant or frail older adult.
Emergency — act now
Drowsiness or unresponsiveness, sunken eyes, inability to drink, a skin pinch taking two seconds or more to flatten, or no urine passed for many hours.
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