Diarrhea is one of the most common causes of dehydration. When you have loose, watery stools multiple times a day, your body loses fluids faster than usual. This can quickly lead to dehydration, especially in young children and older adults.
Understanding how diarrhea causes dehydration and knowing the right ways to replace lost fluids can help you recover faster and avoid serious complications.
Table of Contents
- How Diarrhea Leads to Dehydration
- Signs of Dehydration to Watch For
- The Best Fluids for Rehydration
- Other Helpful Fluids
- Comparing Rehydration Methods
- Special Considerations for Different Groups
- Foods That Help During Recovery
- Additional Treatments That May Help
- Preventing Dehydration from Diarrhea
- When to Seek Medical Help
- The Bottom Line
How Diarrhea Leads to Dehydration
When you have diarrhea, your intestines don’t absorb water properly. This means more water stays in your stool instead of being absorbed into your body. The frequent bowel movements can cause you to lose large amounts of fluids and important minerals called electrolytes.
Dehydration from diarrhea can happen quickly. Young children with diarrhea often present with mild to moderate dehydration requiring immediate treatment (1).
Children under 5 years old are particularly vulnerable. Guidelines emphasize the importance of recognizing dehydration early and providing appropriate treatment in hospital settings (2).
Signs of Dehydration to Watch For
Recognizing dehydration early is important for preventing serious complications. The signs can vary depending on how severe the dehydration is.
Mild to Moderate Dehydration
Common signs of mild to moderate dehydration include:
- Thirst
- Dry mouth and lips
- Less frequent urination
- Dark yellow urine
- Tiredness or feeling weak
- Headache
- Dizziness when standing up
In babies and young children, you might also notice:
- No tears when crying
- Dry diapers for 3 hours or more
- Sunken eyes
- Being less active or playful than usual
Severe Dehydration
Severe dehydration is a medical emergency. Signs include:
- Very dry mouth and lips
- Sunken eyes
- Skin that doesn’t bounce back when pinched
- Little or no urination
- Rapid heartbeat
- Rapid breathing
- Confusion or irritability
- Fainting or feeling like you might pass out
The Best Fluids for Rehydration
Not all fluids are equal when it comes to treating dehydration from diarrhea. The right fluids can help you recover faster and more effectively.
Oral Rehydration Solutions (ORS)
Oral rehydration solutions are specially formulated drinks that contain the right balance of water, salts, and sugar. They’re the most effective treatment for dehydration from diarrhea.
Research shows that ORS can successfully rehydrate over 90% of children with mild to moderate dehydration from diarrhea (1). These solutions work because they contain:
- Glucose (sugar): Helps your intestines absorb water and sodium
- Sodium: Replaces lost salts and helps retain water in your body
- Potassium: Another important electrolyte lost in diarrhea
- Chloride and citrate: Help maintain proper fluid balance
Low-Osmolarity ORS
Recent research has shown that low-osmolarity ORS (with less salt and sugar) may work even better than standard ORS. A large systematic review found that low-osmolarity ORS significantly reduces both stool output and duration of diarrhea compared to standard ORS (3).
In one study of children with diarrhea, those who received hypotonic (low-osmolarity) ORS needed less fluid for maintenance hydration compared to those receiving standard ORS (4).
Rice-Based ORS
Rice-based oral rehydration solutions have shown promising results in treating diarrhea-related dehydration. Studies show that rice-based ORS can substantially reduce stool output compared to standard glucose-based ORS (5).
However, not all rice-based products work equally well. Commercial rice-based ORS formulations may vary in their effectiveness (6).
Other Helpful Fluids
While ORS is the best choice, other fluids can also help with rehydration:
- Clear broths: Chicken or vegetable broth provides fluids and salts
- Coconut water: Contains natural electrolytes
- Diluted fruit juices: Mix with equal parts water to reduce sugar content
- Sports drinks: Can help but often contain too much sugar
Plain water alone isn’t the best choice for rehydration during diarrhea. It doesn’t contain the electrolytes your body needs to hold onto fluids.
Comparing Rehydration Methods
For most people with mild to moderate dehydration, drinking ORS works as well as getting fluids through an IV. But which method is better depends on the situation.
Oral vs. IV Rehydration
A study comparing nasogastric (tube feeding) and intravenous rehydration in children found both methods were safe and effective for treating moderate dehydration (7).
For severe dehydration, IV fluids work faster. A study comparing Ringer’s lactate and normal saline found that while both could be used for rapid intravenous rehydration in children with severe dehydration, there was no significant difference in pH improvement between the two fluids (8).
Special Considerations for Different Groups
Some people need extra care when dealing with dehydration from diarrhea.
Infants and Young Children
Babies and young children can become dehydrated very quickly. They need special attention because:
- Their bodies contain more water relative to their size
- They lose fluids faster than adults
- They can’t tell you when they’re thirsty
For breastfed babies, continue breastfeeding along with ORS. Formula-fed babies can continue their regular formula after initial rehydration.
Severely Malnourished Children
Children with severe malnutrition need special ORS formulations. A study found that hypo-osmolar ORS had beneficial effects in severely malnourished children with dehydrating diarrhea (9).
People with Special Medical Conditions
Some medical conditions require special consideration:
- Diabetes: May need sugar-free rehydration options
- Heart disease: May need to limit sodium intake
- Kidney disease: May need modified electrolyte solutions
Foods That Help During Recovery
What you eat during and after diarrhea can affect your recovery. The right foods can help replace lost nutrients and may even reduce diarrhea symptoms.
The Role of Food in Rehydration
Research shows that eating food doesn’t interfere with oral rehydration therapy. A study in adults with cholera found that food does not reduce the effectiveness of either glucose-based or rice-based ORS (5).
Early refeeding has been studied in children with diarrhea. In one study, full feedings were reintroduced after 6-10 hours of rehydration, and children recovered well (10).
Best Foods During Diarrhea
Some foods can help firm up stools and provide important nutrients:
- Rice and rice water: Easy to digest and may help reduce stool output
- Bananas: Provide potassium and are easy on the stomach
- Toast or crackers: Simple carbohydrates that are easy to digest
- Boiled potatoes: Provide energy and some electrolytes
- Lean proteins: Such as boiled chicken or fish
Foods to Avoid
Some foods can make diarrhea worse:
- Fatty or fried foods
- Dairy products (if lactose intolerant)
- High-fiber foods
- Sugary drinks and foods
- Caffeine and alcohol
Additional Treatments That May Help
Besides rehydration, some treatments may help reduce diarrhea duration and improve symptoms.
Zinc Supplementation
Zinc supplements have been shown to reduce the duration and severity of diarrhea in children. The World Health Organization now recommends zinc along with ORS for treating childhood diarrhea.
In Ethiopia, bundling zinc with ORS improved treatment adherence. The study found that joint adherence to zinc and ORS treatment increased substantially by 14.8 to 15.7 percentage points when the products were bundled together with instructional messages (11).
Probiotics and Other Supplements
Some studies suggest that certain probiotics may help reduce diarrhea duration. However, the evidence varies depending on the type of probiotic and the cause of diarrhea.
Other treatments being studied include:
- Immunoglobulin Y: A specialized antibody that may help with rotavirus diarrhea (12)
- Cholestyramine: May help shorten watery diarrhea duration (10)
Preventing Dehydration from Diarrhea
The best way to prevent dehydration is to start replacing fluids as soon as diarrhea begins. Don’t wait for signs of dehydration to appear.
Clean Water and Sanitation
Many cases of diarrhea can be prevented through better water quality. A study in Bolivia found that point-of-use water treatment and safe storage reduced diarrhea episodes by 44% (13).
Early Treatment
Starting ORS early can prevent mild dehydration from becoming severe. Keep ORS packets at home if you or your children are prone to diarrhea.
Key prevention strategies include:
- Start ORS at the first sign of watery diarrhea
- Continue breastfeeding for infants
- Maintain good hygiene to prevent spread
- Seek medical care if symptoms worsen
When to Seek Medical Help
While most cases of diarrhea and mild dehydration can be treated at home, some situations require medical attention.
See a doctor if you or your child has:
- Signs of severe dehydration
- Blood in the stool
- High fever (over 102°F or 39°C)
- Severe abdominal pain
- Diarrhea lasting more than 3 days in adults or 24 hours in children
- Repeated vomiting that prevents keeping fluids down
Babies under 6 months old with diarrhea should always be seen by a healthcare provider.
The Bottom Line
Dehydration from diarrhea can be serious, but it’s usually preventable and treatable with the right approach. Oral rehydration solutions are the most effective treatment for most cases of dehydration from diarrhea. They work as well as IV fluids for mild to moderate dehydration and are much easier to use at home.
Remember to start rehydration early, continue eating appropriate foods, and seek medical help if symptoms are severe or don’t improve. With proper treatment, most people recover from diarrhea-related dehydration within a few days.