Dialysis can and often does cause or worsen diarrhea, through several overlapping mechanisms ranging from the medications you take alongside treatment to shifts in blood pressure during sessions and changes in the gut’s bacterial environment. Roughly one in five patients starting hemodialysis reports diarrhea, and gut symptoms as a whole affect a majority of people on either form of dialysis. The reasons are varied enough that pinpointing your specific trigger usually requires working through them one by one with your care team.
How Common Is Diarrhea in Dialysis Patients
A Japanese study of 243 patients beginning hemodialysis found that 19% had diarrhea, with infectious diseases and concurrent antibiotic or steroid use flagged as high-risk factors.1Renal Replacement Therapy. Prevalence of diarrhea in end-stage renal disease patients initiating hemodialysis That figure captures only the start of treatment. Gastrointestinal symptoms more broadly are even more prevalent: one study comparing hemodialysis and peritoneal dialysis patients found that 51% of those on hemodialysis reported at least one GI symptom, while 85% of peritoneal dialysis patients did.2PubMed. Peritoneal dialysis patients have higher prevalence of gastrointestinal symptoms than hemodialysis patients
Interestingly, the two types of dialysis seem to produce different symptom profiles. A separate study found that hemodialysis patients actually had a higher rate of diarrhea specifically (about 18%) compared with peritoneal dialysis patients (about 5%), even though peritoneal dialysis patients reported more GI symptoms overall.3PubMed Central. Gastrointestinal symptoms: a comparison between patients undergoing peritoneal dialysis and hemodialysis The reasons for this difference aren’t entirely settled. Hemodialysis involves larger fluid shifts and blood-pressure swings, which affect gut blood flow in ways peritoneal dialysis does not. Meanwhile, peritoneal dialysis patients tend to struggle more with bloating and early fullness from the fluid sitting in their abdomen. Either way, diarrhea is common enough in both groups that it should never be dismissed as unrelated to your treatment.
Medications That Frequently Trigger Loose Stools
If you’re on dialysis, you’re almost certainly also taking a handful of other medications, and several of them are well-known gut irritants. The most common culprits fall into a few categories.
Phosphate Binders
High phosphorus levels are a near-universal problem in dialysis, and phosphate binders are prescribed to nearly every patient. Sevelamer, one of the most widely used binders, carries a meaningfully higher risk of GI side effects compared with calcium-based alternatives. A systematic review and meta-analysis found that sevelamer raised the risk of gastrointestinal adverse events by about 39% compared with calcium salts, with diarrhea, bloating, and constipation all reported.4American Journal of Kidney Diseases. Comparative Efficacy and Safety of Phosphate Binders in Patients With Chronic Kidney Disease: A Systematic Review and Meta-analysis Newer alternatives like bixalomer are associated with fewer GI symptoms than sevelamer, so if your binder is giving you trouble, switching may help.5PubMed. An update on phosphate binders for the treatment of hyperphosphatemia in chronic kidney disease patients on dialysis: a review of safety profiles
Potassium Binders
Sodium polystyrene sulfonate (often sold as Kayexalate) is used to lower dangerously high potassium levels. It’s notorious for gut side effects. A comprehensive review of patients experiencing adverse GI effects from Kayexalate or its calcium counterpart found that diarrhea accounted for about 21% of presenting symptoms, alongside abdominal pain and bloody stools.6PubMed Central. Adverse Gastrointestinal Effects with Kayexalate or Kalimate: A Comprehensive Review Rare but serious GI damage, including bowel necrosis, has also been documented with older potassium binders, though newer agents like sodium zirconium cyclosilicate appear to cause fewer gut problems.7PubMed Central. Clinical utility of patiromer, sodium zirconium cyclosilicate, and sodium polystyrene sulfonate for the treatment of hyperkalemia: an evidence-based review
Calcimimetics
Cinacalcet, used to manage secondary hyperparathyroidism in dialysis patients, frequently causes nausea and vomiting. While vomiting gets the most attention, GI upset from calcimimetics can include diarrhea, and the nausea alone can disrupt eating patterns in ways that destabilize the gut further.8PubMed Central. Clinical and Practical Use of Calcimimetics in Dialysis Patients With Secondary Hyperparathyroidism
Because dialysis patients typically take multiple medications from these categories simultaneously, teasing out which one is responsible can feel like a guessing game. The practical approach is usually to change or stop one medication at a time, with your nephrologist’s guidance, and observe the effect over a week or two.
Blood Pressure Drops and Gut Blood Flow
Hemodialysis removes fluid from the bloodstream rapidly, and blood pressure sometimes drops during or shortly after sessions. This is called intradialytic hypotension, and it doesn’t just make you lightheaded. It also reduces blood flow to the intestines. In its mildest form, that reduced perfusion can cause cramping and loose stools. In its most severe form, it leads to nonocclusive mesenteric ischemia, a condition where the bowel becomes injured due to insufficient blood supply even though no artery is physically blocked.
Nonocclusive mesenteric ischemia is the leading cause of acute abdominal emergencies in the dialysis population, and its early symptoms, including fever, diarrhea, and elevated white blood cell counts, are frustratingly nonspecific.9PubMed Central. Nonocclusive mesenteric ischemia in a patient on maintenance hemodialysis Intensive ultrafiltration and intradialytic hypotension are the usual triggers.10PubMed Central. Acute non-occlusive mesenteric ischemia of the small bowel in a patient started on hemodialysis: a case report A large case-control study found a clear dose-response relationship: the more sessions with significant blood pressure drops (systolic pressure falling below 90), the higher the odds of hospitalized mesenteric ischemia.11PubMed Central. The Relationship between Intradialytic Hypotension and Hospitalized Mesenteric Ischemia: A Case-Control Study
This doesn’t mean every episode of diarrhea after a dialysis session signals ischemia. Most of the time, mild gut underperfusion resolves on its own. But persistent or bloody diarrhea that follows sessions where your blood pressure dropped sharply deserves urgent attention. If you regularly feel faint during dialysis and have diarrhea afterward, tell your team so they can reassess your fluid removal targets and session length.
The Changed Gut Microbiome in Kidney Disease
Even before dialysis starts, advanced kidney disease reshapes the bacterial community living in the intestine. The buildup of uremic toxins in the blood and the dietary restrictions kidney patients follow both favor certain species of bacteria over others, a state researchers call dysbiosis. Studies have confirmed that this microbial shift is accompanied by damage to the intestinal lining itself. The barrier that normally keeps bacteria and their byproducts confined to the gut weakens, allowing bacterial toxins to leak into the bloodstream.12PubMed Central. CKD impairs barrier function and alters microbial flora of the intestine: a major link to inflammation and uremic toxicity
This leaky-gut dynamic feeds a cycle. Kidney disease promotes dysbiosis and barrier breakdown, which worsens systemic inflammation, which in turn can further harm the kidneys and the gut.13PubMed Central. The Impact of CKD on Uremic Toxins and Gut Microbiota Dialysis partially clears uremic toxins but does not fully correct the microbial imbalance. The net result is an intestinal environment that is chronically inflamed and more prone to diarrhea, bloating, and cramping than a healthy gut would be.14Kidney International. The intestinal microbiota, a leaky gut, and abnormal immunity in kidney disease
Infections That Hit Dialysis Patients Harder
Dialysis patients are immunocompromised to a degree, making them more vulnerable to gut infections that a healthy immune system might fight off quickly. The most worrisome is Clostridioides difficile infection (often still referred to as C. diff), a bacterial infection that causes watery diarrhea, fever, and abdominal pain. A review of records from over 400,000 incident dialysis patients found that about 4.25% developed a first episode of C. difficile infection. Most of those patients had been hospitalized or in an ICU within the prior 90 days, and recurrence hit nearly a quarter of them.15PubMed. Clostridium difficile infection in dialysis patients Having end-stage kidney disease needing dialysis was itself an independent risk factor for developing the infection, with one analysis showing over thirteen times the adjusted odds compared with earlier stages of kidney disease.16PubMed Central. Clostridium difficile-associated diarrhea in dialysis patients
Parasitic infections also deserve mention, especially in regions where they are endemic. Research has found that routine stool testing in dialysis patients with diarrhea can catch parasites like Cryptosporidium, Giardia, and Entamoeba histolytica that might otherwise go undiagnosed. Specialized staining methods and antigen-detection kits are more reliable than standard stool exams for picking up these organisms.17Saudi Medical Journal. Investigation of intestinal parasites in dialysis patients If your diarrhea persists despite medication adjustments, asking whether infection has been adequately ruled out is a reasonable step.
When Diabetes Compounds the Problem
A large share of people on dialysis have diabetes as the underlying cause of their kidney failure. Diabetes introduces its own set of GI problems on top of everything dialysis does. Long-standing diabetes often damages the autonomic nerves that control gut motility, a condition called diabetic autonomic neuropathy. The consequences range from gastroparesis (delayed stomach emptying) to chronic diarrhea and fecal incontinence.18PubMed Central. Diabetic autonomic neuropathy of the gastrointestinal tract
In diabetic kidney disease specifically, the sources of diarrhea multiply. Nerve damage can slow the gut and promote bacterial overgrowth, while disturbed gastrointestinal hormone secretion and impaired pancreatic function add further triggers. Poor fat absorption from pancreatic dysfunction can cause greasy, loose stools. Gallbladder nerve involvement can lead to bile-salt diarrhea. And damage to the rectal sphincter nerves can produce urgency and incontinence that feel like diarrhea even when stool consistency is normal.19Exploratory Research and Hypothesis in Medicine. A Systematic Review of Gastrointestinal Manifestations in Diabetic Nephropathy For dialysis patients with diabetes, treating the diarrhea often means addressing the diabetic neuropathy as well, not just the dialysis-related causes.
Small Intestinal Bacterial Overgrowth
Separate from the broad dysbiosis described earlier, some dialysis patients develop small intestinal bacterial overgrowth, or SIBO, where bacteria that normally live in the colon colonize the small intestine. A study of patients with chronic renal failure found SIBO in about 36% of them, and more than half of those with abnormal small-bowel motility patterns had SIBO. The researchers noted that disturbed intestinal motility might explain diarrhea in some of these patients, though symptoms and bacterial overgrowth didn’t always line up neatly.20Digestion. Patients with Chronic Renal Failure Have Abnormal Small Intestinal Motility and a High Prevalence of Small Intestinal Bacterial Overgrowth SIBO is treatable with targeted antibiotics, which makes it worth testing for if diarrhea is persistent and other causes have been excluded.
Water Quality and Dialysate Contamination
Hemodialysis exposes your blood to large volumes of treated water through the dialysis membrane. If that water contains bacterial endotoxins or chemical contaminants, it can trigger systemic inflammatory responses that include GI symptoms. Outbreaks linked to water-quality failures in dialysis units have been documented repeatedly since the 1960s, causing hundreds of cases of illness and some deaths in the United States alone.21PubMed Central. Hemodialysis and water quality Modern dialysis centers are held to strict water-treatment standards, so this is uncommon. But if multiple patients at the same unit develop diarrhea simultaneously, contaminated water or dialysate should be investigated.
Why Diarrhea During Dialysis Is More Dangerous Than Usual
For most healthy people, a bout of diarrhea is unpleasant but self-limiting. For dialysis patients, the stakes are higher. Diarrhea causes fluid and electrolyte losses that are normally balanced by the kidneys, but your kidneys aren’t doing that job. Potassium, sodium, and bicarbonate can swing unpredictably when diarrhea and dialysis are happening in the same timeframe. In peritoneal dialysis patients, severe diarrhea combined with the fluid removal from peritoneal exchanges can lead to dangerously low blood volume, electrolyte imbalances, and metabolic acidosis.22Journal of Medical Case Reports. Melanosis coli in a peritoneal dialysis patient: a case report
Newer medications currently under study for phosphate control, like tenapanor, work by blocking sodium absorption in the gut, which inherently softens stools and can cause diarrhea as a side effect. Whether this drug-induced diarrhea is a nuisance or a clinical concern depends on the patient: in someone who tends to retain too much fluid between sessions, the extra fluid loss might actually reduce the amount that needs to be removed during dialysis. But in someone who already runs dry between sessions, that same fluid loss could worsen low blood pressure during treatment.23Hemodialysis International. Tenapanor Beyond Phosphate: Gut Sodium Transport, Stool Transit Time, and Volume Balance in Dialysis Patients This is a good example of why the same symptom can mean different things in different dialysis patients, and why blanket advice is hard to give.
What You Can Do About It
Because the causes are so varied, there’s no single fix. But the troubleshooting process has a logic to it:
- Review your medications: Phosphate binders (especially sevelamer), potassium binders, antibiotics, and iron supplements are the most common pharmaceutical triggers. Your nephrologist can often switch to alternatives that are gentler on the gut.
- Get tested for infection: C. difficile testing should be done early, especially if you’ve been hospitalized or on antibiotics recently. Ask about parasitic screening if standard tests come back negative.
- Check your fluid removal targets: If diarrhea consistently follows dialysis sessions where your blood pressure dropped, the ultrafiltration rate or dry weight target may need adjusting.
- Consider SIBO testing: A breath test can detect bacterial overgrowth in the small intestine, which is treatable with a short course of antibiotics.
- Assess diabetic neuropathy: If you have diabetes and chronic diarrhea that doesn’t respond to the above steps, autonomic nerve damage to the gut may be a factor. Managing blood sugar more tightly and specific medications for diabetic gastroparesis or bile-salt diarrhea can help.
You might also see advice about probiotics. Research into probiotics, prebiotics, and synbiotics for gut health in kidney disease has produced limited and conflicting results so far.24Seminars in Dialysis. Feeling gutted in chronic kidney disease (CKD): Gastrointestinal disorders and therapies to improve gastrointestinal health in individuals CKD, including those undergoing dialysis They’re unlikely to cause harm, but the evidence isn’t strong enough to recommend them as a primary treatment. Keeping a symptom diary that logs when diarrhea occurs relative to dialysis sessions, meals, and medication doses remains one of the most useful things you can bring to your care team.
Oral Nutritional Supplements and Timing of Meals
Dialysis patients often face protein-energy wasting, and oral nutritional supplements are frequently recommended to combat malnutrition. But these supplements can themselves trigger GI symptoms, including diarrhea, nausea, and postprandial hypotension, particularly when consumed during or just before a dialysis session. This has made their use somewhat controversial, and policies about in-center nutrition vary from one dialysis clinic to the next.25PubMed Central. Effects of oral nutritional supplements on the nutritional status and inflammatory markers in patients on maintenance dialysis: a systematic review and meta-analysis of randomized clinical trials If you find that a supplement shake or a heavy meal close to your session reliably sets off diarrhea, spacing food intake further from treatment, or switching supplement formulations, is a straightforward adjustment worth trying. Your dietitian can help find a product and timing that maintains your caloric and protein intake without destabilizing your gut.