Antibiotic-Associated Diarrhea: Symptoms, Causes, Treatment & Complete Guide

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 17, 2026

About 1 in 5 people who take antibiotics develops diarrhea. Most cases are mild and settle on their own, but diarrhea that starts days to weeks later — especially with belly pain or fever — can signal a C. difficile infection that needs a doctor.

Quick Answer

Antibiotic-associated diarrhea is passing loose, watery stools three or more times a day after taking antibiotics, affecting about 1 in 5 people who take them. Mild cases usually end within days. Serious cases, often caused by C. diff, need a doctor. Call your healthcare professional if diarrhea lasts over two days, or comes with pain, fever, dehydration or bloody stools.

What the research says

• Probiotics reduce the risk, but only some strains and doses work. A meta-analysis of 42 randomized trials (11,305 adults) found probiotics taken with antibiotics cut the risk of antibiotic-associated diarrhea by 37% (risk ratio 0.63; 95% CI 0.54–0.73; moderate-quality evidence); higher doses worked better, only certain species, mainly Lactobacillus and Bifidobacterium, were effective, and studies with a low baseline risk showed no difference (Goodman et al., BMJ Open, 2021) [3].

• In children, the benefit was large, with a caution. A Cochrane review of 33 trials (6,352 children) found diarrhea in 8% of children given probiotics versus 19% of controls (RR 0.45; 95% CI 0.36–0.56; moderate certainty), with no serious adverse events attributed to probiotics in the 24 trials that reported them — though observational studies outside the review have reported serious events in severely debilitated or immunocompromised children (Guo et al., Cochrane Database of Systematic Reviews, 2019) [4].

• Risk climbs in the sickest patients. A 2026 meta-analysis in critically ill patients found antibiotic-associated diarrhea in 29% (95% CI 24%–35%) and C. difficile-associated diarrhea in 12% (95% CI 7%–17%); cephalosporin use (OR 1.67; 95% CI 1.31–2.12) and combined antibiotic use (OR 2.44; 95% CI 1.96–3.04) were among the risk factors (Wei et al., Journal of Gastroenterology and Hepatology, 2026) [5].

Antibiotic-Associated Diarrhea at a Glance

Aspect	Summary
What it is	Loose, watery stools 3+ times a day after taking antibiotics [1]
How common	About 1 in 5 people who take antibiotics
Mild case timing	Begins within hours or a few days; ends on its own within days or after treatment ends [1]
Serious case timing	Usually begins several days to two months after starting the antibiotic [1]
Most common serious cause	Clostridioides difficile (C. diff) infection in the large intestine [1]
Three causes	Direct tissue harm, helpful bacteria destroyed, harmful bacteria grow out of control [1]
Most at-risk antibiotics	Cephalosporins, fluoroquinolones, penicillins, clindamycin, carbapenems, macrolides [1]
Key warning signs	Diarrhea over 2 days, belly pain, fever, dehydration, black/tarry/bloody stools [1]
Main complication	Severe dehydration (life-threatening) [1]
Treatment	Fluids, switching or stopping the antibiotic, C. diff antibiotics, restoring healthy bacteria, surgery if severe [2]

What Is Antibiotic-Associated Diarrhea?

Antibiotic-associated diarrhea is passing loose, watery stools three or more times a day after taking medicines called antibiotics — medicines used to treat bacterial infections [1]. About 1 in 5 people who take antibiotics gets antibiotic-associated diarrhea [1].

Most cases are mild. Mild cases tend to begin shortly after taking antibiotics, and mild diarrhea usually ends after a few days on antibiotics or shortly after finishing the treatment [1]. But diarrhea that doesn't end on its own or is more serious usually requires stopping the antibiotic — and you may need to be treated with a different antibiotic [1].

The distinction between the mild, expected version and the serious version matters more than anything else in this condition. The serious version is a sign of bacterial disease in the large intestine, and most often it points to Clostridioides difficile — the same bacterium behind pseudomembranous colitis.

What are the symptoms of antibiotic-associated diarrhea?

Antibiotic-associated diarrhea usually causes mild symptoms that clear on their own, but serious cases, most often caused by C. diff, can lead to dehydration.

Mild Symptoms

For most people, antibiotic-associated diarrhea causes mild symptoms:

Symptom	What to look for
Loose stools	Watery, unformed stools
Three or more times a day	The frequency that defines the condition

Mild antibiotic-associated diarrhea may begin within hours or within a few days of starting an antibiotic [1]. In most cases it clears on its own.

Symptoms of More-Serious Diarrhea

Serious diarrhea often begins several days to two months after starting the medicine [1]. It happens when there is bacterial disease in the large intestine, most often caused by Clostridioides difficile (C. diff) [1]. Symptoms may include:

Symptom	Detail
Frequent or severe diarrhea	Beyond the mild "loose stools" picture
Pain and cramping in the lower belly	A sign the large intestine itself is involved
Low fever	Sign of infection
Nausea	Digestive upset
Loss of appetite	Reduced desire to eat
Dehydration	The loss of fluids and the minerals they carry

Dehydration Warning Signs

Because diarrhea drains fluids and the minerals they carry, dehydration is the complication to watch for. In adults it shows up as extreme thirst or dryness in the mouth, very little or no urine, dark urine, dizziness, lightheadedness or extreme tiredness, and sunken cheeks or eyes [1].

In young children, watch for: no wet diapers for three or more hours, no tears when crying, a sunken soft spot in the skull, and unusual drowsiness [1].

When should you see a doctor about antibiotic-associated diarrhea?

A number of conditions can cause diarrhea, so use these four triggers as your rule: call your healthcare professional if you have diarrhea that lasts more than two days, diarrhea with belly pain, fever or other severe symptoms, symptoms of dehydration, or stools that are black, tarry or bloody [1].

What causes antibiotic-associated diarrhea?

Antibiotic-associated diarrhea happens when antibiotics disrupt the colon's healthy balance of bacteria, letting harmful bacteria, most often C. diff, thrive.

The Three Causes

Antibiotic-associated diarrhea may be related to three mechanisms:

Cause	What happens
Direct harm	Direct harm from an antibiotic to tissues of the large intestine [1].
Helpful bacteria destroyed	Destruction of helpful bacteria that play a role in the digestive system [1].
Harmful bacteria take over	C. difficile or other harmful bacteria that grow out of control without enough helpful bacteria to keep the harmful bacteria in check [1].

The healthy colon normally hosts a balance of bacteria that keep each other in check. Antibiotics can disrupt that balance, and in the disruption harmful bacteria — most often C. diff — get the chance to thrive and cause disease.

Antibiotics Most Likely to Cause Diarrhea

Nearly all antibiotics can cause antibiotic-associated diarrhea [1]. The antibiotics most often involved include:

Antibiotic family	Examples
Cephalosporins	Cefixime (Suprax), others
Fluoroquinolones	Ciprofloxacin (Cipro), levofloxacin
Penicillins	Amoxicillin, ampicillin
Lincosamides	Clindamycin (Cleocin)
Carbapenems	Imipenem, meropenem
Macrolides	Azithromycin, erythromycin

What are the risk factors for antibiotic-associated diarrhea?

Antibiotic-associated diarrhea can occur in anyone who takes an antibiotic, though some factors raise the risk. Other risk factors include:

Risk factor	Detail
Past antibiotic-associated diarrhea [1]	Having had it in the past raises the chance it happens again
Being an infant [1]	The youngest digestive systems are more vulnerable
Being 65 or older [1]	Age increases risk
Long hospital stays [1]	More exposure and disrupted gut balance
Living in a nursing home [1]	Similar exposure factors
Having a serious illness [1]	A weakened body fights back less effectively
Taking a proton pump inhibitor [1]	Medicines that lower stomach acids raise the risk

What complications can antibiotic-associated diarrhea cause?

One of the most common complications of any type of diarrhea is extreme loss of fluids and electrolytes (dehydration) [1]. Severe dehydration can be life-threatening [1]. Its signs and symptoms include a very dry mouth, intense thirst, little or no urination, dizziness, and weakness [1].

The serious C. diff-driven form of this condition carries further risks — toxic megacolon, bowel perforation, and death — and needs urgent medical care.

How can antibiotic-associated diarrhea be prevented?

Antibiotic-associated diarrhea can be prevented with three practices that are outlined below.

Preventive measure	What to do
Take antibiotics only when needed	Don't use antibiotics unless your healthcare professional says you need them. Antibiotics can treat bacterial infections, but they won't help viral infections, such as colds and flu [1].
Wash your hands frequently	Wash your hands before and after eating or meal preparation, after using the toilet, after handling garbage, and when your hands are clearly dirty. If you're getting care at home or in the hospital, ask all the people who care for you to wash their hands or use an alcohol-based hand sanitizer [1].
Tell your healthcare professional about your history	If you have had antibiotic-associated diarrhea or C. difficile before, say so. Having had either condition in the past increases the chance that antibiotics will cause that same reaction again — and your health professional may be able to choose a different antibiotic for you [1].

How is antibiotic-associated diarrhea diagnosed?

Diagnosing the cause of your diarrhea starts with a conversation. Your healthcare professional will likely ask you questions about your symptoms, recent diet, recent use of antibiotics, and other questions about your health history [2]. A sample of your stool may be sent to a lab for testing [2] — especially if a C. difficile or other bacterial infection is suspected.

How is antibiotic-associated diarrhea treated?

Treatment for antibiotic-associated diarrhea depends on how bad the symptoms are.

Mild Cases

Mild symptoms are likely to clear up within a few days after starting antibiotics or shortly after the treatment ends. You may need to switch to a different antibiotic.

C. difficile Infection

Treating a C. difficile infection or a related bacterial infection requires stopping the original antibiotic [2]. Your healthcare professional likely will prescribe antibiotics to kill the C. difficile bacteria [2]. You also might be asked to stop taking medicines that lower stomach acids [2]. Additional treatments may be needed for recurring C. difficile infections — these may include medicines or a procedure to restore healthy bacteria in the colon [2]. Severe disease may require surgery [2].

What self-care helps antibiotic-associated diarrhea?

Antibiotic-associated diarrhea symptoms can be managed at home with three self-care measures.

Self-care step	Details
Drink enough fluids	Drink plenty of water and fluids that have electrolytes, such as broths or sports drinks or other bottled drinks with electrolytes. Oral rehydration solutions with water, electrolytes and sugar are available without a prescription [2]. For infants and children with diarrhea, ask a healthcare professional about using an oral rehydration solution, such as Pedialyte, to replace fluids [2].
Ask about antidiarrheal medicines	Teenagers and adults may be able to take an antidiarrheal medicine, such as bismuth subsalicylate (Kaopectate, Pepto-Bismol, others). This generally is not recommended for children [2]. Ask your healthcare professional before using any antidiarrheal medicine because some should not be used if you have C. difficile or another bacterial infection of the large intestine [2].
Consider probiotics — with eyes open	Some people take supplements called probiotics to restore the balance of healthy bacteria in their guts. The research is mixed on whether probiotics ease symptoms of antibiotic-associated diarrhea [2]. Taking probiotics probably won't do harm, but people with weakened immune systems should not use probiotic supplements [2].

How should you prepare for an antibiotic-associated diarrhea appointment?

If you have diarrhea after taking an antibiotic, make an appointment with the healthcare professional who prescribed the antibiotic [2].

Before the appointment, make a list of:

• Your symptoms and when they began, including any that may not seem related.

• Key personal information, such as major stresses or recent life changes and recent stays in a hospital or a nursing home.

• All medicines, vitamins or supplements you take, with doses and reasons.

• Your questions.

• If you have recently taken an antibiotic, its name and dose — and if you have completed the course, when you took the last dose.

Questions to ask your healthcare professional include:

• What tests do I need?

• What is the best course of action?

• Are there restrictions I should follow?

• Are there foods and drinks I should avoid?

• Can I take an antidiarrheal medicine?

Be sure to ask all the questions you have. Your doctor will likely ask:

• Can you describe your stools? (Your health professional may have a chart with images to help you describe them.)

• How often do you have them?

• Do you have a history of gut diseases such as ulcerative colitis or Crohn's disease?

• Have you recently been around anyone with diarrhea?

• Have you changed your diet recently?

• Do you work in a nursing home, hospital or day care setting?

• Have you recently traveled?

Conclusion

• Common and usually mild. About 1 in 5 people who take antibiotics experience it, and most mild cases clear within days on their own.

• Timing and severity tell you which case you have. Mild diarrhea starts within hours or days and fades; serious diarrhea starts days to two months after starting the antibiotic and brings belly pain, fever, and dehydration — the C. diff pattern.

• Your history and your fluids matter. If you have had this condition or C. diff before, tell your doctor so a safer antibiotic can be chosen; at home, fluids and electrolytes are your first line of defense.

Never hesitate to call a healthcare professional if diarrhea lasts more than two days or your stools are black, tarry, or bloody.

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Frequently Asked Questions

What is antibiotic-associated diarrhea?

Antibiotic-associated diarrhea is passing loose, watery stools three or more times a day after taking antibiotics — medicines used to treat bacterial infections. About 1 in 5 people who take antibiotics gets it.

How soon after starting antibiotics does it begin?

Mild cases usually begin within hours or a few days of starting the antibiotic. More serious cases — most often caused by C. difficile in the large intestine — often begin several days to two months after starting the medicine.

Does mild antibiotic-associated diarrhea need treatment?

Mild symptoms are likely to clear up within a few days after starting antibiotics or shortly after the treatment ends. You may need to switch to a different antibiotic, but the diarrhea itself often resolves on its own.

What are the warning signs that it is serious?

Frequent or severe diarrhea, pain and cramping in the lower belly, low fever, nausea, loss of appetite, and dehydration. Call your healthcare professional if diarrhea lasts more than two days, comes with belly pain, fever or dehydration symptoms, or if stools are black, tarry or bloody.

Why do antibiotics cause diarrhea at all?

Three mechanisms: direct harm from the antibiotic to large intestine tissues, destruction of helpful digestive bacteria, and C. difficile or other harmful bacteria growing out of control once the helpful bacteria that keep them in check are gone.

Can I take an antidiarrheal medicine?

Teenagers and adults may be able to take bismuth subsalicylate (Kaopectate, Pepto-Bismol), but this is generally not recommended for children. Ask your healthcare professional before using any antidiarrheal medicine — some should not be used if you have C. difficile or another bacterial infection of the large intestine.

Will it happen again next time I take antibiotics?

Having had antibiotic-associated diarrhea or C. difficile in the past increases the chance that antibiotics will cause the same reaction again. Tell your healthcare professional — they may be able to choose a different antibiotic for you.

Related Reading

Probiotics: Benefits, Types, Foods and Side Effects explains what probiotics do and when they help.

Antibiotics: Types, Uses, Side Effects and Resistance explains how antibiotics work and how to use them safely.

References

1. Mayo Clinic Staff. Antibiotic-associated diarrhea - Symptoms and causes. Mayo Clinic. Sept. 20, 2025. https://www.mayoclinic.org/diseases-conditions/antibiotic-associated-diarrhea/symptoms-causes/syc-20352231

2. Mayo Clinic Staff. Antibiotic-associated diarrhea - Diagnosis and treatment. Mayo Clinic. Sept. 20, 2025. https://www.mayoclinic.org/diseases-conditions/antibiotic-associated-diarrhea/diagnosis-treatment/drc-20352237

3. Goodman C, Keating G, Georgousopoulou E, et al. Probiotics for the prevention of antibiotic-associated diarrhoea: a systematic review and meta-analysis. BMJ Open. 2021;11(8):e043054. PMID: 34385227. https://doi.org/10.1136/bmjopen-2020-043054

4. Guo Q, Goldenberg JZ, Humphrey C, et al. Probiotics for the prevention of pediatric antibiotic-associated diarrhea. Cochrane Database Syst Rev. 2019;4(4):CD004827. PMID: 31039287. https://doi.org/10.1002/14651858.CD004827.pub5

5. Wei Q, Lu G, Diao H, et al. The incidence and risk factors of antibiotic-associated diarrhea in critically ill patients: a systematic review and meta-analysis. J Gastroenterol Hepatol. 2026;41(4):1147-1162. PMID: 41804814. https://doi.org/10.1111/jgh.70315

Medical disclaimer

This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare provider with any questions about a medical condition.