Diarrhea for Two Weeks: Why It's Lasting and How to Find Your Specific Cause

If you've had diarrhea for two weeks, you're past the point where "wait and see" is a reasonable plan. Persistent diarrhea - loosely defined as diarrhea lasting more than two weeks - is a signal that something ongoing is driving it, and it's worth taking seriously.

The hard part is that the list of possible causes is long. Infections, food intolerances, IBS, inflammatory bowel disease, medications, celiac disease - any of these could explain what's happening. And generic information about causes doesn't tell you which one applies to you.

This article covers the main reasons diarrhea can persist for two weeks or longer, with particular attention to dietary triggers - because food-related causes are more common than many people realize, and they're also something you can investigate yourself. It also explains when you need to see a doctor (spoiler: if you've hit two weeks, that's now), and how tracking what you eat and how you feel can help you build a clearer picture of what's going on.

Important: Two weeks of diarrhea warrants a medical evaluation. Please see your doctor if you haven't already - especially if you have blood in your stool, a fever, significant weight loss, or signs of dehydration. The tracking approach in this article is a complement to medical care, not a replacement for it.

What Does "Persistent Diarrhea" Actually Mean?

Medically, diarrhea is classified by how long it lasts:

• Acute diarrhea: Less than two weeks - usually a short-lived infection or stomach bug
• Persistent diarrhea: Two to four weeks - the category you're in now
• Chronic diarrhea: Four weeks or more - indicates an underlying ongoing condition

Reaching the two-week mark means the cause is unlikely to be a simple virus that will resolve on its own. According to the Mayo Clinic, persistent and chronic diarrhea are typically caused by conditions that require investigation - whether that's a lingering infection, a gut condition, or something in your diet that your body is consistently reacting to.

Why Is My Diarrhea Lasting Weeks? The Main Causes

Could it be a lingering infection?

Viral gastroenteritis (stomach flu) usually clears within a few days, but some infections hang around. Parasitic infections - particularly Giardia - are a well-known cause of diarrhea that persists for two weeks or longer. Giardia is contracted through contaminated water or food, and without treatment it can cause weeks of loose stools, bloating, and fatigue.

Bacterial infections can also cause persistent symptoms, particularly if the gut's bacterial balance has been disrupted. If you've traveled recently, eaten at a new restaurant, or had any event that could have exposed you to contaminated food or water, infection should be high on the list to rule out. Your doctor can test for this.

Could it be a reaction to medication?

Antibiotics are a common trigger. They disrupt the gut microbiome and can cause diarrhea that lasts well beyond the course of treatment. Other medications - including certain antacids, metformin, and some heart medications - can also cause ongoing loose stools. If you started a new medication around the time your diarrhea began, that timing is worth noting and discussing with your prescribing doctor.

Could it be IBS?

Irritable bowel syndrome, particularly IBS-D (the diarrhea-predominant subtype), is one of the most common causes of persistent diarrhea. IBS is a functional gut condition - meaning the gut is structurally normal but doesn't work the way it should - and it's heavily influenced by both stress and diet.

Research suggests that more than half of IBS patients report that specific foods worsen their symptoms. Common triggers include high-FODMAP foods (a group of fermentable carbohydrates found in onions, garlic, wheat, legumes, and certain fruits), dairy, and caffeine. IBS is a diagnosis of exclusion, meaning other causes need to be ruled out first.

Could it be inflammatory bowel disease?

Crohn's disease and ulcerative colitis are chronic inflammatory conditions of the gut that can cause persistent diarrhea, often accompanied by abdominal cramping, blood in the stool, and weight loss. These conditions require medical diagnosis and management - if you're seeing blood in your stool or experiencing significant pain, get medical attention promptly.

For anyone dealing with Crohn's specifically, tracking food alongside symptoms may also help in understanding flare patterns. Our article on food diary for Crohn's disease covers this in depth.

Could it be celiac disease or gluten sensitivity?

Celiac disease is an autoimmune condition where gluten (a protein in wheat, barley, and rye) triggers an immune response that damages the small intestine. One of its most common symptoms is chronic diarrhea. Non-celiac gluten sensitivity can produce similar symptoms without the same level of intestinal damage. Both conditions respond to a gluten-free diet, but celiac disease requires a formal diagnosis before starting the diet (testing is less accurate once you've removed gluten).

Could it be lactose intolerance?

Lactose intolerance - the inability to properly digest lactose, the sugar in dairy products - is one of the most prevalent food intolerances worldwide. When undigested lactose reaches the large intestine, gut bacteria ferment it, producing gas, bloating, cramping, and diarrhea. Research published in PMC notes that lactose malabsorption is particularly common in people who also have IBS.

What makes lactose intolerance tricky to spot is that the reaction depends on how much dairy you consume. A small amount may cause no symptoms; a larger amount triggers the response. If you've been eating dairy regularly throughout your two weeks of diarrhea, it's worth testing whether removing it makes a difference - ideally under medical guidance. You can also read more about lactose intolerance symptoms to see if your experience matches the pattern.

Could it be other dietary triggers?

Beyond lactose and gluten, a range of dietary factors can contribute to persistent loose stools:

• Fructose malabsorption: Excessive fructose from fruit, fruit juice, honey, or high-fructose corn syrup can exceed the gut's absorption capacity and trigger diarrhea
• Sugar alcohols: Sorbitol, xylitol, and similar sweeteners (common in "sugar-free" products and chewing gum) have a well-known laxative effect
• Caffeine: A stimulant that accelerates gut transit - if you've increased your coffee, tea, or energy drink intake, this could be a contributing factor
• High-fat foods: Fat slows digestion but can also trigger bile acid release, which may speed up gut transit in some people
• Artificial sweeteners: Some people find that certain artificial sweeteners cause digestive disruption, though the evidence is variable

A 2024 Lancet Gastroenterology study found that dietary interventions were more effective than medication for managing IBS symptoms - which underscores how significant food can be in driving gut symptoms. The challenge is that the relevant food is different for each person.

How Do You Find Out Which Cause Applies to You?

Here's the key question that generic articles about "causes of diarrhea" don't answer: of all these possible causes, how do you figure out which one is actually driving your symptoms?

The answer is systematic tracking.

Tracking what you eat, when you eat it, and what happens to your digestion afterward allows patterns to emerge that would otherwise be impossible to see. A stomach bug doesn't follow a food pattern. A reaction to lactose does. IBS triggered by high-FODMAP foods does. The pattern is the diagnostic clue.

What to track

If you want to use tracking to investigate dietary causes of persistent diarrhea, here's what matters:

1. What you ate - including all ingredients, not just the meal name ("chicken pasta" isn't useful; "pasta with garlic, onion, and cream sauce" is)
2. When you ate it - timing relative to symptoms matters; some food reactions happen within 30 minutes, others take 24-48 hours
3. Your symptoms - frequency, consistency, and severity of bowel movements, plus any accompanying symptoms like bloating, cramping, or fatigue
4. Stress levels - relevant for IBS particularly, where stress can amplify gut reactivity
5. Medications and supplements - especially anything new

The goal is to look for repeating patterns: does diarrhea consistently follow meals containing dairy? Does it get worse on high-stress days regardless of what you ate? Does removing gluten for a week change anything?

This is the kind of analysis that a food and symptom diary makes possible - and it's the kind of information that also helps your doctor. Rather than saying "I've had diarrhea for two weeks," you can say "I've had diarrhea for two weeks and I've noticed it's consistently worse within a couple of hours of eating dairy or wheat-based meals." For more on building an effective diarrhea food diary, see our guide on food diary for diarrhea.

DietSleuth was built precisely for this kind of investigation. You log what you eat, and the app's AI automatically breaks meals down into their individual ingredients - so you're tracking at the ingredient level without having to do the manual work. It then looks for correlations between specific foods, ingredients, and symptoms over time, surfacing patterns that are genuinely difficult to spot by memory alone.

Start Your Free Trial of DietSleuth

When to See a Doctor - and What to Tell Them

If you've had diarrhea for two weeks, you should see a doctor now. This is the point at which medical evaluation is warranted, not optional.

Seek urgent or emergency care if you have:

• Blood in your stool (red or black/tarry)
• A fever of 102°F (39°C) or higher
• Severe abdominal or rectal pain
• Signs of dehydration: dizziness, dark urine, dry mouth, little or no urination
• Significant unexplained weight loss

For a standard (non-emergency) doctor's appointment, prepare by noting:

• When the diarrhea started and whether it's been continuous or intermittent
• Any recent travel, new foods, or events that might have preceded it
• Any new medications or supplements
• Whether you've noticed any relationship between specific foods and worsening symptoms
• Any accompanying symptoms like fatigue, bloating, or joint pain

The more specific your account, the faster you can get to a useful diagnosis. This is where even a week of tracked food and symptom data can make a real difference.

What Can You Do Right Now?

While you're waiting for your appointment - or if you've already seen a doctor and are waiting for test results - here are some reasonable steps:

Stay hydrated. Diarrhea depletes fluids and electrolytes quickly. Water is essential; oral rehydration solutions (available at pharmacies) are useful if symptoms are severe.

Note obvious dietary patterns. Even before tracking formally, think back over the past two weeks. Is there a food you've been eating regularly that's new to your diet, or that you've been eating in larger quantities? Dairy, gluten, high-FODMAP foods, and excessive caffeine are the most common dietary drivers worth considering.

Start a food and symptom log. Even a simple notes app is better than nothing. Write down meals and symptoms as they happen - memory is unreliable, especially over days and weeks.

Don't self-diagnose and start eliminating foods without medical guidance. Particularly important for celiac disease: a gluten-free diet before testing will make the tests inaccurate. Get tested first.

What Your Doctor Might Investigate

Depending on your symptoms and history, your doctor may order:

• Stool tests - to check for infection, parasites, bacteria, and inflammatory markers
• Blood tests - to check for celiac antibodies, signs of inflammation, thyroid issues, and nutritional deficiencies
• Colonoscopy or endoscopy - if IBD, microscopic colitis, or other structural causes are suspected
• Hydrogen breath test - for lactose intolerance or small intestinal bacterial overgrowth (SIBO)

These tests help rule in or out the medical causes. What they can't always tell you is which specific foods are driving ongoing symptoms - particularly with conditions like IBS or non-celiac gluten sensitivity, where the diagnosis doesn't automatically identify your personal triggers. That's where ongoing tracking continues to be useful, even after you have a diagnosis.

The Bigger Picture: Tracking as an Ongoing Tool

For many people with persistent or recurrent diarrhea, finding the cause isn't a single moment - it's a process. You might get a diagnosis of IBS and still need to identify which specific foods trigger your symptoms. You might test negative for celiac but still find that reducing gluten helps. You might discover that your symptoms are driven by a combination of factors - stress plus certain foods plus poor sleep.

Research supports a personalized approach: a 2025 study in Scientific Reports on low-FODMAP diets found that while the approach helps many people with IBS, individual responses vary considerably. The Monash University FODMAP research group reports that the low-FODMAP diet reduces symptoms in roughly 3 in 4 people with IBS - but identifying your specific trigger foods within the FODMAP group still requires systematic reintroduction and tracking.

Your body's data is the most relevant data there is. Tracking what you eat and how you feel is how you collect it.

This content is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider before making changes to your diet or health routine. If you have been experiencing diarrhea for two weeks or longer, please seek medical evaluation.

Sources

1. Mayo Clinic. "Diarrhea - Symptoms and Causes." https://www.mayoclinic.org/symptoms/diarrhea/basics/definition/sym-20050926
2. Cleveland Clinic. "Chronic Diarrhea: What It Is, Causes & Treatment Options." https://my.clevelandclinic.org/health/diseases/24311-chronic-diarrhea
3. Chey WD, et al. "Dietary Considerations in the Irritable Bowel Syndrome." PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC4944381/
4. El-Salhy M, et al. "Dietary fiber in irritable bowel syndrome." PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC5467063/
5. Storhaug CL, et al. "Country, regional, and global estimates for lactose malabsorption in adults." Referenced via PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC8746545/
6. National Institute of Diabetes and Digestive and Kidney Diseases. "Symptoms & Causes of Diarrhea." https://www.niddk.nih.gov/health-information/digestive-diseases/diarrhea/symptoms-causes
7. Monash University FODMAP Research. "About FODMAPs and IBS." https://www.monashfodmap.com/about-fodmap-and-ibs/
8. Algera JP, et al. "Low FODMAP diet reduces symptoms in patients with irritable bowel syndrome." Scientific Reports, 2025. https://www.nature.com/articles/s41598-025-01163-3
9. Bellini M, et al. "What Are the Pearls and Pitfalls of the Dietary Management for Chronic Diarrhoea?" PMC, 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8143080/
10. Johns Hopkins Medicine. "Diarrhea." https://www.hopkinsmedicine.org/health/conditions-and-diseases/diarrhea