By Eddie Khoriaty, BPharm, R.Ph., C.Ph.
Diarrhea can leave you wondering whether it was something you ate, a stomach bug, or a medication you’re taking. One of the first questions I would ask is: What changed?
Did you start a new medicine or supplement, increase a dose, or try a new protein shake or sugar-free snack? Have you traveled recently, eaten out, or been around someone who was sick? Those details can help narrow down the possibilities. Timing matters too. Diarrhea that started yesterday needs a different approach from loose stools that keep coming back.
This guide explains common causes, how medicines and supplements can contribute, and what may help. We’ll also cover hydration, over-the-counter options, and the warning signs that mean it’s time to seek medical care.
At a Glance
Diarrhea generally means loose or watery stools three or more times a day, or more often than is normal for you. It’s worth paying attention to stool consistency and urgency too, rather than just counting trips to the bathroom.
How long it lasts helps narrow down the possible causes:
These terms describe the pattern; they are not instructions to wait that long before getting help. Contact your clinician if diarrhea lasts more than two days, and seek help sooner if you have blood or black, tarry stool, severe pain, high fever, or signs of dehydration.
Wondering whether it’s food poisoning or a stomach bug? Our Food Poisoning or Stomach Bug guide explains how they can differ, with practical advice on hydration and symptoms to watch for.
The cause isn’t always obvious, and sometimes more than one thing contributes. These are some of the possibilities worth considering:
The timing and your full medication and supplement list can help narrow things down. Something you’ve taken for years still matters, especially if the dose changed or you recently added another product.
Start with a simple question: What changed? Think back to the days before your symptoms began. These details are worth noting:
Eating triggers the gastrocolic reflex, a normal signal that tells your colon to move stool along. If you need the bathroom shortly after a meal, it doesn’t mean the food you just ate has already passed through you.
That reflex can be stronger in people with IBS. Certain foods and drinks, including lactose, sugar alcohols, caffeine, and high-fat meals, may also contribute to loose stools or urgency.
Pay attention to whether it happens after particular foods or after nearly every meal. Symptoms that keep returning, wake you at night, or come with unintentional weight loss or greasy stools deserve a medical evaluation.
Morning coffee, nicotine, breakfast, and stress can all affect bowel activity. For some people, the normal urge to go after waking or eating is especially strong.
Medicine timing may offer another clue. Note what you take in the evening and first thing in the morning, including supplements and laxatives.
If the pattern keeps returning, a record of meals, medicines, and bowel movements can help your clinician or pharmacist spot possible connections. You don’t need to wait until you’ve completed a tracker to ask for help.
Prostaglandins help the uterus contract during your period, but they can also increase bowel activity. That can mean looser or more frequent stools around the start of menstruation.
A familiar pattern that settles as your period progresses is different from a new or lasting change. Talk with your clinician if symptoms are unusually disruptive or come with severe pain, very heavy bleeding, fever, or fainting.
Yes, and it’s easy to overlook something you take every day. The timing can offer a clue, especially if diarrhea started after adding a product or increasing a dose. Sometimes several things contribute rather than one obvious cause.
Antibiotics can cause diarrhea, including from an infection called C. difficile. Let your clinician know if diarrhea develops during or after an antibiotic course, especially if it is frequent, severe, or accompanied by fever or abdominal pain.
Metformin is another common contributor. Magnesium supplements can loosen stools too, depending on the form, dose, and your sensitivity. Berberine and high-dose vitamin C may also cause digestive side effects.
Other possibilities include colchicine, some antidepressants, nonsteroidal anti-inflammatory drugs (NSAIDs), and laxatives. Check the ingredients in gummies, powders, and shakes as well. Sugar alcohols can contribute even when they aren’t the main ingredient.
I would want to review the whole list, including prescriptions, over-the-counter medicines, supplements, and products labeled “natural.” Don’t stop a prescription on your own. Write down when symptoms began and any recent changes so your pharmacist or prescriber can help you decide what needs attention.
Diarrhea is a common side effect of medicines such as Ozempic, Wegovy, Mounjaro, and Zepbound. It often happens when treatment begins or after a dose increase, although not everyone experiences it.
Still, I wouldn’t automatically assume the GLP-1 is the only cause. Metformin, magnesium, berberine, sugar alcohols, and lactose in protein shakes may also contribute. A stomach bug or food poisoning can happen while you’re taking these medicines too.
Hydration deserves particular attention. If your appetite is smaller and you’re drinking less, diarrhea can make it harder to replace the fluids you lose. Significant dehydration can affect kidney function.
Let your prescriber know if symptoms keep returning, worsen after a dose increase, or interfere with eating and drinking. Don’t change your dose on your own, and check with your pharmacist or prescriber before adding an over-the-counter anti-diarrheal.
Seek prompt medical care for blood or black, tarry stool, severe or persistent abdominal pain, repeated vomiting, inability to keep fluids down, fainting, or much less urine.
For more pharmacist-written guidance on side effects, nutrition, and questions to ask your prescriber, visit our GLP-1 Resource Center.
Start with fluids. Diarrhea causes you to lose water and electrolytes. Sip frequently rather than trying to drink a large amount at once, especially if your stomach feels unsettled. For repeated watery stools, a commercial oral rehydration solution can help replace those losses. Mix powders exactly as directed. If you have kidney disease, diabetes, or a prescribed fluid restriction, ask your clinician which option is appropriate.
Eat as your appetite allows. You don’t need to stay on a strict BRAT diet of bananas, rice, applesauce, and toast. Those foods may be easy to tolerate, but they don’t provide everything you need. Smaller portions of familiar foods can be a good starting point, then return to your usual balanced diet as tolerated.
Ease up on possible triggers. Alcohol, caffeine, very fatty meals, and sugar alcohols can worsen symptoms. Dairy may also be harder to tolerate temporarily, even if it usually agrees with you. You don’t need to cut out everything; pay attention to what seems to make your symptoms worse.
For recurring symptoms, ask before adding fiber. Soluble fiber, such as psyllium, sometimes helps improve stool consistency. But diarrhea that keeps returning needs an evaluation, rather than simply adding another product to manage it.
An anti-diarrheal may ease symptoms without addressing the cause. The comparison below covers two common options. Before choosing either, there are a few additional precautions worth knowing.
Ask your pharmacist before taking loperamide if you have a heart rhythm condition or take medicines that affect heart rhythm.
Follow the package directions. If symptoms worsen or diarrhea lasts more than two days, stop using it and contact your clinician.
Along with the cautions in the comparison below, check with your pharmacist or clinician if you take medicines for diabetes, gout, or arthritis, have an ulcer, or have a history of bleeding problems.
Bismuth can interfere with the absorption of tetracycline antibiotics, including doxycycline. Your pharmacist can explain how to space the doses.
Children and teenagers who have chickenpox or flu-like symptoms, or are recovering from them, should not take it because of the risk of Reye’s syndrome.
It can temporarily darken your tongue and stool. However, don’t assume black, tarry stool is harmless, especially if it began before taking the medicine or comes with weakness, dizziness, or pain.
As a pharmacist, I would review your symptoms and medication list before recommending either option. Replacing lost fluids remains the priority.
Ask about your medicines when you’re dehydrated. Repeated diarrhea or vomiting can change how safely you take certain medicines. If you take water pills, some blood pressure medicines, metformin, SGLT2 inhibitors, or lithium, ask your pharmacist or prescriber what to do during an illness. Include over-the-counter pain relievers such as ibuprofen and naproxen in that conversation. Follow any sick-day plan you’ve already been given; otherwise, get advice before changing your prescriptions.
If you take a birth control pill and have vomiting or severe or prolonged diarrhea, check your pill’s instructions and ask your pharmacist whether you need backup contraception.
They work differently, and the right choice depends on your symptoms and what else you take.
Neither replaces hydration. Warning signs need medical attention. This adult comparison is a quick reference; follow the full cautions above and the product label.
Probiotics aren’t interchangeable. The benefit depends on the specific strain or combination of strains, the dose, and what it has been studied for. Research on one strain doesn’t automatically apply to another product or blend.
Saccharomyces boulardii and Lacticaseibacillus rhamnosus GG (formerly Lactobacillus rhamnosus GG) are among the most studied probiotics for preventing antibiotic-associated diarrhea. Some studies show benefit, but results vary, and professional guidelines don’t all recommend the same approach. A probiotic is not a substitute for evaluating diarrhea that develops during or after antibiotics.
If you are seriously ill, have a weakened immune system, or have a central venous catheter, speak with your clinician before taking a probiotic.
GILA Balance does not contain those two strains. It is designed for daily digestive support, not to prevent or treat diarrhea. Our guide, How to Choose a Probiotic, explains what to look for on the label and why the strain matters.
Daily Digestive Support
Looking for a probiotic for your everyday routine? GILA Balance combines four probiotic strains with prebiotic FOS for daily digestive support.
Explore GILA BalanceNot intended to prevent or treat diarrhea. If symptoms are ongoing, speak with your clinician before adding a supplement.
Some people alternate between loose stools and constipation, particularly with IBS. Bloating can occur with either.
There is another possibility worth knowing about, especially in older adults: watery stool can leak around a buildup of hard, impacted stool. This is called overflow diarrhea, and it can be mistaken for ordinary diarrhea.
If you’ve been constipated and then begin passing watery stool, don’t keep adding an anti-diarrheal without getting advice. An examination and medication review may be needed to understand what’s happening. Our Constipation and Bloating guides cover these patterns in more detail.
For a sudden stomach illness, use the Stomach Illness Hydration and Symptom Log. For symptoms that keep returning or alternate between diarrhea and constipation, use the Digestive Regularity Tracker.
Record when symptoms happen, how often you go, and whether stools are watery, loose, or hard. Include meals, fluids, medicines, supplements, and symptoms such as pain, nausea, or dizziness.
The record doesn’t need to be perfect to be useful. Bring what you have to your pharmacist or clinician, and don’t wait to finish a tracker before seeking care.
Contact a clinician promptly if you have:
Fainting, confusion, severe weakness, or severe pain may require emergency care.
Diarrhea that regularly wakes you from sleep or comes with unintentional weight loss also needs evaluation, even if it doesn’t feel urgent.
Seek advice sooner if you are pregnant, over 65, have a weakened immune system, or have another condition that makes dehydration more concerning. For infants and young children, contact their clinician early rather than following the adult timeline.
When diarrhea starts suddenly, focus on replacing lost fluids and ask what changed. If it keeps returning, the timing and your full medication and supplement list may tell us more than guessing which food caused it.
Over-the-counter products can help in some situations, but they shouldn’t be used to cover up warning signs. If symptoms persist or you’re struggling to stay hydrated, getting advice is the next step.
Find pharmacist-written guides on diarrhea, constipation, bloating, and probiotics, plus practical tools to help you track digestive symptoms.
Many short episodes improve within a few days. Contact your clinician if diarrhea lasts more than two days, and seek help sooner for blood or black, tarry stool, severe pain, high fever, or signs of dehydration. A pattern that keeps returning also deserves evaluation.
Blood in the stool, black, tarry stool, severe pain, frequent vomiting, or trouble staying hydrated need prompt medical attention. Contact your clinician for six or more loose stools in a day, a high fever, or diarrhea lasting more than two days. Diarrhea that wakes you at night or comes with unintentional weight loss should also be evaluated.
Eating triggers a normal reflex that tells the colon to move stool along. That reflex can be stronger with IBS, while certain foods and drinks may contribute to loose stools or urgency. It doesn’t mean the meal you just ate has already passed through you.
Coffee, breakfast, nicotine, stress, and medicine timing may all play a role. Note whether symptoms begin before or after eating, drinking coffee, or taking your medicines. If the pattern continues, share those details with your clinician.
Prostaglandins that help the uterus contract can also increase bowel activity. This may cause looser stools around the start of your period. A new or unusually severe pattern, especially with significant pain, fever, fainting, or very heavy bleeding, should be discussed with your clinician.
Yes. Antibiotics, metformin, magnesium, berberine, high-dose vitamin C, and laxatives are some examples. Sugar alcohols in gummies, powders, and protein products can contribute too. Ask your pharmacist to review the full list, and don’t stop a prescription on your own.
Yes. Diarrhea is a common side effect of medicines such as Ozempic, Wegovy, Mounjaro, and Zepbound, often when treatment begins or the dose increases. Other medicines, foods, or an infection may contribute, so don’t assume the GLP-1 is the only cause. Contact your prescriber if symptoms persist, worsen, or interfere with hydration.
A sports drink supplies fluid and some electrolytes, but it isn’t formulated the same way as an oral rehydration solution. For repeated watery stools or significant fluid loss, a commercial oral rehydration product is generally a better fit. Ask your clinician which option to use if you have kidney disease, diabetes, or a fluid restriction.
Loperamide, sold as Imodium, can help some adults with uncomplicated watery diarrhea. Check with a clinician first if you have fever, blood or mucus in your stool, severe pain, or diarrhea during or after antibiotics. Follow the label dose exactly, and seek advice if symptoms worsen or last more than two days.
Some specific probiotics have evidence for reducing the risk of antibiotic-associated diarrhea, but the benefit depends on the strain and situation. A daily probiotic blend shouldn’t be assumed to have the same effect. Diarrhea during or after antibiotics needs medical advice rather than simply adding a probiotic.
Yes. Some people alternate between loose and hard stools. Watery stool can also leak around impacted stool, creating what’s called overflow diarrhea. If watery stools follow a period of constipation, get advice before repeatedly taking an anti-diarrheal.
Diarrhea can overlap with other digestive symptoms, and medicines, supplements, and food choices may all play a role. These guides take a closer look:
Why Am I So Bloated? Explore common causes of bloating, including food triggers, trapped gas, and changes in bowel habits.
How to Choose a Probiotic Learn how to compare strains, CFU counts, formulations, and storage requirements.
What Is Elemental Magnesium? Understand the difference between a magnesium compound’s weight and its elemental amount, and why the form and dose matter.
Why Am I Constipated? Learn about hard stools, incomplete emptying, and why watery stools can sometimes occur alongside constipation.
Sources accessed October 2, 2026.
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The information provided in this article is intended for educational purposes only and should not be considered medical advice. It is not intended to diagnose, treat, cure, or prevent any disease, or to replace the advice of your physician or other qualified healthcare provider.
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