Replacing lost fluid is the single most important thing you can do when diarrhea strikes, and everything else, from dietary choices to medication, plays a supporting role around that core priority. Most episodes of acute diarrhea in otherwise healthy adults resolve on their own within a few days, but the combination of dehydration, electrolyte loss, and discomfort makes active treatment worthwhile. The right approach depends on how severe the episode is, what’s causing it, and whether you’re dealing with a child, an older adult, or someone in between.
Why Fluids Come First
Your intestines handle a remarkable volume of liquid every day. Between what you drink, what you eat, and what your body secretes into the gut during digestion, roughly nine liters of fluid pass through the intestinal tract in a 24-hour period. Normally, absorption outpaces secretion and most of that fluid gets reabsorbed. Diarrhea flips that balance: fluid secretion overwhelms absorption, and water pours out in your stool instead of returning to your bloodstream.1PubMed Central. Intestinal secretory mechanisms and diarrhea The causes vary, from infectious toxins that trigger active chloride secretion to osmotic effects from poorly absorbed sugars, and a single episode often involves more than one of these mechanisms at once.2JCI Insight. Intestinal ion transport and the pathophysiology of diarrhea
The practical takeaway is that dehydration, not the diarrhea itself, is what makes people dangerously sick. Mild dehydration causes thirst, dry mouth, and fatigue. Moderate dehydration brings dizziness, reduced urine output, and sunken eyes in children. Severe dehydration can cause confusion, rapid heartbeat, and organ damage. Replacing fluid and electrolytes, particularly sodium and potassium, is the treatment that saves the most lives worldwide and the step you should start immediately.
What to Drink and How Oral Rehydration Works
Plain water helps, but it doesn’t replace the sodium, potassium, and glucose your body is losing. That’s where oral rehydration solutions come in. ORS works because glucose and sodium are absorbed together across the intestinal lining, and each molecule of sugar transported pulls along hundreds of water molecules with it. Research has shown that the sodium-glucose cotransporter in the intestine accounts for roughly five liters of water absorption per day under normal conditions.3PubMed. Cotransport of water by the Na+/glucose cotransporter This pathway keeps working even when the gut is actively secreting fluid from infection, which is why ORS can rehydrate someone with cholera who would otherwise need an IV.
The current WHO-recommended formula uses a reduced-osmolarity solution (250 mOsm/L or less), which performs better than older, saltier versions. In children hospitalized with diarrhea, reduced-osmolarity ORS led to fewer unscheduled IV fluid infusions, lower stool volume, and less vomiting compared to the older formula, without increasing the risk of dangerously low sodium levels.4Cochrane Database of Systematic Reviews. Reduced osmolarity oral rehydration solution for treating dehydration caused by acute diarrhoea in children One multicenter trial found the reduced formula cut the need for unscheduled IV therapy by about a third.5PubMed. Multicenter, randomized, double-blind clinical trial to evaluate the efficacy and safety of a reduced osmolarity oral rehydration salts solution in children with acute watery diarrhea
You can buy pre-mixed ORS packets or premade solutions at most pharmacies. If those aren’t available, a homemade version using six level teaspoons of sugar and half a teaspoon of salt dissolved in one liter of clean water provides a reasonable approximation. Sports drinks are less ideal because they contain too much sugar and too little sodium, but they’re better than nothing if ORS isn’t on hand. Avoid fruit juices, sodas, and caffeinated drinks during active diarrhea: the high sugar content can actually worsen symptoms through osmotic effects, and caffeine is a mild intestinal stimulant.
For adults with mild diarrhea who are otherwise healthy, sipping broth, diluted juice, or water with crackers may be enough. But for children, older adults, or anyone showing signs of moderate dehydration, a proper ORS is the better choice.
What to Eat During and After an Episode
The old advice to fast or stick to clear liquids for days has fallen out of favor. A Cochrane review comparing early refeeding (within hours) to delayed refeeding found no evidence that eating soon after diarrhea begins increases the risk of complications like vomiting, IV fluid needs, or persistent illness.6PubMed Central. Early versus Delayed Refeeding for Children with Acute Diarrhoea Your gut heals faster with nutrients coming in, especially calories and protein, so there’s no reason to go hungry if you can tolerate food.
That said, not all foods are equally friendly to an irritated digestive tract. The general pattern that works for most people:
- Well-tolerated foods: white rice, plain toast, bananas, boiled potatoes, plain crackers, cooked carrots, lean chicken or fish, and oatmeal. These are low in fiber, low in fat, and easy to digest.
- Foods to limit temporarily: greasy or fried foods, dairy products (especially milk), raw vegetables, beans and legumes, spicy dishes, and anything with sugar alcohols (sorbitol, mannitol) commonly found in sugar-free gum and candy.
Bananas deserve special mention because they’re rich in potassium, which you lose heavily during diarrhea, and they contain pectin, a soluble fiber that absorbs excess water in the gut. Research in children with persistent diarrhea found that cooked green banana and pectin both led to significant improvements. By day three, roughly 55-59% of children receiving banana or pectin had recovered compared to just 15% of controls, and by day four those recovery rates climbed to around 78-82%.7Gastroenterology. Clinical studies in persistent diarrhea: Dietary management with green banana or pectin in Bangladeshi children The benefit appears to come from improved intestinal permeability and increased water absorption in both the small and large intestine.8PubMed. Green banana and pectin improve small intestinal permeability and reduce fluid loss in Bangladeshi children with persistent diarrhea
Apple pectin has shown similar effects. A study of 255 children with acute diarrhea found that a product containing apple pectin and chamomile significantly improved symptoms compared to placebo. Pectin-rich foods, whether from bananas, apples, or carrots, may be among the most useful dietary additions during recovery.
Over-the-Counter Medications
Two types of nonprescription medication dominate pharmacy shelves for diarrhea, and they work through different mechanisms.
Loperamide
Loperamide (sold as Imodium and generics) slows intestinal motility, giving your gut more time to absorb water and nutrients. It’s effective for mild to moderate diarrhea, and a systematic review found no proof that antibiotics are significantly more effective than loperamide for treating uncomplicated traveler’s diarrhea.9PubMed. Systematic review of loperamide: No proof of antibiotics being superior to loperamide in treatment of mild/moderate travellers’ diarrhoea When used alongside an antibiotic for more serious bacterial infections, loperamide roughly halved the duration of diarrhea and cut the number of loose stools dramatically.10PubMed. Ciprofloxacin and loperamide in the treatment of bacillary dysentery
The main concern with loperamide is using it when you have a serious inflammatory infection with high fever or bloody stools. In those situations, slowing the gut can theoretically trap bacteria and toxins inside, potentially causing complications like toxic megacolon. However, the American College of Gastroenterology notes this association is rare and mostly seen when the inflammatory infection goes untreated with antibiotics. When an antimicrobial drug is also given, the risk is very low.11American Journal of Gastroenterology. ACG Clinical Guideline: Diagnosis, Treatment, and Prevention of Acute Diarrheal Infections in Adults The standard adult dose is 4 mg initially, then 2 mg after each loose stool, up to 16 mg per day. Loperamide is generally not recommended for young children without medical supervision.
Bismuth Subsalicylate
Bismuth subsalicylate (Pepto-Bismol and generics) works differently. Its salicylate component has antisecretory effects, meaning it helps reduce the amount of fluid your intestines actively pump out. The bismuth component has direct antimicrobial activity against some gut pathogens.12PubMed. Bismuth subsalicylate in the treatment and prevention of diarrheal disease It’s milder than loperamide and is often recommended as a first-line option for mild traveler’s diarrhea. The downsides: it can turn your tongue and stool black (harmless but alarming if you’re not expecting it), and it shouldn’t be used by anyone allergic to aspirin, taking blood thinners, or in children recovering from viral infections due to the risk of Reye’s syndrome.
Prescription and Specialized Medications
Beyond what’s available over the counter, several prescription options exist for specific situations.
Racecadotril
Racecadotril is an antisecretory drug available by prescription in many countries (though not in the United States). It works by blocking an enzyme called enkephalinase, which reduces the secretion of water and electrolytes into the gut without slowing motility. In a trial of children with acute watery diarrhea, racecadotril cut 48-hour stool output by about 46% compared to placebo and shortened the median duration of diarrhea from roughly 52-72 hours down to 28 hours.13PubMed. Racecadotril in the treatment of acute watery diarrhea in children Because it doesn’t slow gut movement, it avoids the bloating and constipation that loperamide sometimes causes.
Antibiotics
Most diarrhea is viral and doesn’t benefit from antibiotics. But when bacteria are the culprit, especially in moderate-to-severe traveler’s diarrhea, febrile illness, or dysentery with bloody stools, antibiotics can shorten illness considerably. Azithromycin is currently the preferred first-line choice because it works against a broad range of gut pathogens, including Campylobacter, which has become increasingly resistant to fluoroquinolones in many parts of the world.14PubMed Central. Antibiotic Therapy for Acute Watery Diarrhea and Dysentery For mild cases, antibiotics are generally not recommended because the illness resolves on its own and unnecessary antibiotic use contributes to resistance.15PubMed Central. Travelers’ Diarrhea: A Clinical Review
Adsorbent Clays
Diosmectite, a medicinal clay widely used in Europe and parts of Asia, works by physically binding to bacteria, toxins, and viruses in the gut. Laboratory studies have shown it can inhibit rotavirus replication and reduce the chloride secretion that drives watery diarrhea.16PubMed Central. Mechanisms of antidiarrhoeal effects by diosmectite in human intestinal cells It also modifies the protective mucus layer lining the intestines and reduces gut inflammation.17PubMed Central. Anti-diarrheal effects of diosmectite in the treatment of acute diarrhea in children: a review Diosmectite is not available in every market, and it’s less commonly discussed in North American guidelines, but it represents a treatment category worth knowing about if you encounter it while traveling.
Probiotics and Zinc
Two supplements have accumulated enough evidence to be worth considering during an episode of diarrhea, especially in children.
Probiotics
Not all probiotics are equal for diarrhea. The strains with the most consistent evidence are Lactobacillus rhamnosus GG and Saccharomyces boulardii, a beneficial yeast. Reviews of the evidence suggest these strains can shorten the duration of acute diarrhea by roughly one day.18Journal of Clinical Gastroenterology. Probiotics for Prevention and Treatment of Diarrhea A head-to-head trial in Indian children found that L. rhamnosus GG reduced the mean duration of diarrhea by about 19 hours compared to standard care and shortened hospital stays by nearly a full day, while S. boulardii showed a trend toward benefit that didn’t reach statistical significance in that particular study.19International Journal of Clinical Trials. Comparative, randomized-controlled trial on efficacy and safety of Lactobacillus rhamnosus GG and Saccharomyces boulardii in treatment of acute diarrhea in Indian children (COMPARE-GG trial)
The same two strains also show promise for preventing antibiotic-associated diarrhea, the loose stools that develop in some people taking antibiotics because the drugs disrupt normal gut bacteria. If you’ve been prescribed antibiotics and want to reduce that risk, starting a probiotic containing one of these strains at the beginning of your antibiotic course is a reasonable step.
Zinc Supplementation
Zinc plays a direct role in maintaining the intestinal lining: it restores the integrity of the gut barrier, supports immune responses against intestinal pathogens, and blocks certain chloride channels involved in fluid secretion.20Cochrane Database of Systematic Reviews. Oral zinc for treating diarrhoea in children In children, zinc supplementation consistently reduces both the duration and severity of diarrhea episodes, and the WHO recommends it as part of standard treatment for childhood diarrhea in low- and middle-income countries.21PubMed Central. Zinc Fortification and Supplementation to Reduce Diarrhea in Children: A Literature Review Lower doses in the range of 5 to 10 mg are preferred for young children to minimize vomiting, a common side effect at higher doses. For well-nourished adults in high-income countries, the evidence for therapeutic zinc supplementation during diarrhea is thinner, but ensuring adequate zinc intake through diet is still sensible.
When to See a Doctor
Most acute diarrhea can be managed at home. But certain signs warrant medical attention promptly:
- Bloody or black stools: could signal an invasive bacterial infection or another serious condition.
- High fever: temperatures above 38.5°C (101.3°F) alongside diarrhea suggest a more aggressive infection.
- Signs of severe dehydration: very dark urine, dizziness on standing, confusion, or no urine output for many hours.
- Duration beyond a few days: diarrhea lasting more than three days in adults, or more than 24 hours with signs of dehydration in young children, should be evaluated.
- Vulnerable populations: infants under three months, older adults with multiple health conditions, pregnant women, and immunocompromised individuals all have less margin for error.
In children, hospitalization is warranted for severe dehydration, severe malnutrition, a toxic or lethargic appearance, persistent vomiting that prevents oral rehydration, or suspected surgical conditions.22PubMed. Management of acute diarrhea in emergency room
Treating Diarrhea in Older Adults
Elderly individuals face disproportionate risk from diarrheal illness. Multiple medications, weaker immune defenses, lower baseline nutritional status, and chronic conditions like heart failure or kidney disease all narrow the window between “uncomfortable” and “dangerous.” Dehydration sets in faster and hits harder in this group, and electrolyte imbalances can trigger cardiac arrhythmias or worsen kidney function.23PubMed. Diarrheal diseases in the elderly
Clostridioides difficile infection is a particular concern in older adults, especially those in hospitals or long-term care facilities who’ve recently received antibiotics. C. difficile thrives when normal gut bacteria are disrupted, and it causes a particularly stubborn form of diarrhea that can recur. For this population, the emphasis is on careful fluid and electrolyte monitoring, cautious use of antibiotics only when clearly needed, and infection control measures to prevent spread in institutional settings.
What Happens After the Diarrhea Stops
For most people, recovery is straightforward: symptoms resolve, appetite returns, and the gut goes back to normal within a week. But a subset of people develop lingering digestive symptoms after an acute infection. This condition, called post-infectious irritable bowel syndrome, likely involves persistent low-grade inflammation, changes in gut permeability, and altered gut bacteria.24PubMed Central. Post-infectious irritable bowel syndrome Symptoms can include cramping, bloating, and alternating diarrhea and constipation lasting weeks to months after the original infection clears.
A common worry is that infection has caused lasting lactose intolerance, leading people to permanently avoid dairy. Research specifically examining this question found that bacterial gastroenteritis did not cause persistent lactose intolerance in people who tolerated dairy before the illness. Blanket advice to avoid dairy after an infection appears unnecessary for most people.25PubMed. Is lactose intolerance implicated in the development of post-infectious irritable bowel syndrome or functional diarrhoea in previously asymptomatic people? That said, temporarily cutting back on dairy for a few days while the gut recovers is reasonable since the brush-border enzymes that digest lactose can be transiently reduced during acute illness. The key word is “temporarily.” If you tolerated milk before you got sick, you’ll almost certainly tolerate it again.
Prevention Through Hygiene
Once you’ve dealt with an episode of diarrhea, you’d understandably prefer not to repeat it. The single most effective preventive measure is handwashing with soap. A Cochrane review found that hand-washing promotion in schools and daycare centers prevented roughly a third of diarrhea episodes in high-income countries, and community-level handwashing programs in lower-income settings prevented about a quarter of episodes.26PubMed Central. Hand washing promotion for preventing diarrhoea That effect is consistent across different study designs and different pathogens.27PubMed Central. Water, sanitation and hygiene for the prevention of diarrhoea
Water treatment, such as boiling, filtering, or using chlorine tablets, also appears to reduce diarrheal illness, though some researchers note the effect may be partly inflated by placebo effects in unblinded studies. For travelers headed to regions with unreliable water infrastructure, sticking to bottled or treated water, avoiding ice made from tap water, peeling fruits yourself, and eating food served hot remain the practical playbook. These aren’t glamorous interventions, but they remain among the most powerful tools for preventing the kinds of infections that cause diarrhea in the first place.