Diarrhea lasting a full week has moved beyond the typical stomach bug, which usually clears up on its own in two to four days. At this point, you’re in the gray zone between acute diarrhea (under seven days) and what doctors call persistent diarrhea (two to four weeks). The causes range from infections that take longer to clear, to medications, food intolerances, and conditions you may not have considered. Understanding what’s behind it helps you figure out whether you can ride it out or need testing.
Infections That Last Longer Than a Stomach Bug
Most viral stomach infections wrap up in a few days, so if you’re still dealing with loose stools at the one-week mark, a virus is less likely to be the culprit. Parasites and certain bacteria are the more common infectious causes of prolonged diarrhea.
Giardia is one of the most frequent parasitic causes. It’s picked up through contaminated water, including streams and lakes that look clean, and symptoms typically begin one to two weeks after exposure. Once they start, they last two to six weeks on average, and in some people they persist for years. The diarrhea tends to be greasy and foul-smelling, often with bloating, gas, and nausea. Cryptosporidium is another waterborne parasite with a similar timeline. Both are common culprits behind “traveler’s diarrhea” that drags on well past the trip.
On the bacterial side, Campylobacter, Salmonella, certain strains of E. coli, and Clostridioides difficile (C. diff) can all cause diarrhea that stretches beyond a week. C. diff deserves special attention because it often develops after a course of antibiotics. The antibiotics kill off normal gut bacteria, allowing C. diff to overgrow, which can lead to severe, watery, and sometimes bloody diarrhea. If your symptoms started during or shortly after taking antibiotics, this is a strong possibility.
Medications as a Hidden Cause
Nearly any medication can cause diarrhea as a side effect, but some are far more likely to do it. If you started a new drug in the weeks before your symptoms began, that’s worth examining.
The most common offenders include:
- Antibiotics, which disrupt normal gut bacteria and can trigger diarrhea that persists after you finish the course
- Metformin, a widely prescribed diabetes medication known for causing ongoing GI upset, especially in the first weeks of use
- NSAIDs like ibuprofen and naproxen
- Magnesium-containing antacids, which draw water into the intestines
- Proton pump inhibitors used for heartburn and acid reflux
- Herbal teas and supplements, particularly those containing senna or other natural laxative ingredients
Medication-related diarrhea won’t resolve on its own if you keep taking the drug. It typically improves within days of stopping or switching, though you should talk to the prescriber before making changes.
Food Intolerances and Dietary Triggers
Unlike a food allergy, which involves an immune reaction and usually causes symptoms quickly, a food intolerance means your body lacks the enzymes needed to properly digest something. Lactose intolerance is the most common example. If you’re eating the triggering food regularly, you can have diarrhea that seems continuous, stretching across days or weeks without an obvious pattern.
Fructose (found in high amounts in some fruits, honey, and processed foods) and sugar alcohols like sorbitol (used in sugar-free gum and candy) are other frequent triggers. The diarrhea from these tends to come with bloating and gas. If your diet hasn’t changed recently, it’s still possible to develop an intolerance over time, particularly to lactose, which many adults gradually lose the ability to digest.
Post-Infectious Irritable Bowel Syndrome
Sometimes a stomach infection resolves, but the diarrhea doesn’t. This is called post-infectious IBS, and it happens because the original infection disrupts the balance between your gut bacteria and immune system, triggering ongoing inflammation. The infection itself is gone, but the gut hasn’t returned to normal.
This can be frustrating because stool tests come back negative. There’s no active infection to treat, yet symptoms persist. About half of post-infectious IBS cases resolve on their own, but the timeline is long: six to eight years in many cases. If you had a confirmed or suspected stomach bug and the diarrhea has continued well past when the infection should have cleared, this is a realistic explanation.
Less Obvious Causes Worth Considering
Celiac disease, inflammatory bowel disease (Crohn’s disease and ulcerative colitis), and hyperthyroidism can all present with diarrhea that lasts a week or more. These conditions tend to come with other symptoms: unintended weight loss, fatigue, abdominal pain, or blood in the stool. They won’t resolve without treatment, so persistent symptoms that don’t have an obvious trigger warrant investigation.
Stress and anxiety can also cause diarrhea that lasts longer than you’d expect. The gut and brain communicate constantly, and sustained psychological stress can speed up intestinal contractions, leading to loose stools. If you’ve been through a particularly stressful period and no other cause is apparent, this connection is worth considering.
What Testing Looks Like
For diarrhea lasting over seven days, the standard first step is a stool test. Many labs now use an infectious diarrhea panel that checks for 14 different viruses, bacteria, and parasites from a single stool sample, including C. diff. This replaces the older approach of ordering separate stool cultures and parasite exams.
If the panel comes back negative and diarrhea continues past two weeks, the cause is likely non-infectious. At that point, testing shifts toward blood work for celiac disease or thyroid problems, and potentially a colonoscopy if inflammatory bowel disease is suspected. If you have a history of recent international travel and an initial negative result, additional microscopy for less common parasites may be ordered.
Staying Hydrated While You Wait It Out
A week of diarrhea can cause significant fluid and electrolyte loss. The warning signs of dehydration include dark-colored urine, urinating less than usual, dry mouth, dizziness, and skin that doesn’t flatten back right away after being pinched. Clear or pale urine is a reliable sign you’re keeping up with fluid loss.
Water alone doesn’t replace the sodium and potassium you’re losing. A simple oral rehydration solution recommended by the WHO uses just half a teaspoon of salt and two tablespoons of sugar dissolved in about four cups of water. You can also make a juice-based version with three-quarters cup of apple juice, three and a quarter cups of water, and half a teaspoon of salt. Sip steadily throughout the day rather than drinking large amounts at once.
Dehydration is especially dangerous for young children and older adults. For children, no wet diaper in three or more hours, crying without tears, or unusual drowsiness are signs that need prompt medical attention. For adults, a fever over 102°F, blood or black color in the stool, severe abdominal pain, or signs of significant dehydration all warrant a same-day visit.