A heart problem can cause diarrhea, though it is rarely the first explanation doctors consider. The heart and the gut depend on the same blood supply, so when the heart struggles, the bowel can feel it. In practice, though, the pills taken for the heart are more often behind the diarrhea than the heart itself.
How a Struggling Heart Affects the Gut
When the right side of the heart can’t keep up, pressure in the veins rises and blood backs up into the liver and intestines. The bowel wall can become swollen and waterlogged, and a waterlogged wall absorbs food and fluid less well. Bloating, poor appetite and loose stools can therefore come with worsening heart failure. A swollen gut may also absorb water pills taken by mouth less well, so the swelling in your legs may get worse at the same time.
A second route is low flow. When the heart pumps too little blood, the body narrows the vessels to the gut to protect the brain and heart. The bowel can then run short of oxygen, and in severe cases the tissue can die.1Cleveland Clinic Journal of Medicine. Mesenteric ischemia: Recognizing an uncommon disorder and distinguishing among its causes This usually happens during a serious illness such as shock or a severe flare of heart failure, not in stable heart disease.2Cleveland Clinic Journal of Medicine. Mesenteric ischemia: Recognizing an uncommon disorder and distinguishing among its causes
Well-controlled heart failure does not usually upset the bowel. New diarrhea in a stable patient more often points to a medicine change or an infection.
A stomach bug usually comes on suddenly with vomiting or fever and fades within days. Heart-driven gut trouble builds gradually over days to weeks, alongside other signs of fluid build-up. More swelling, a rising weight on the scale, or needing extra pillows to sleep point toward the heart, while fever and sick contacts point toward an infection. A person with heart failure can also catch a stomach bug, so a doctor sorts it out with an exam and sometimes blood tests. If gut symptoms and heart-failure warning signs show up together, call the heart team promptly, because a medicine adjustment is often needed.
Heart Medicines That Can Cause Diarrhea
Digoxin, a heart-rhythm and heart-failure pill, causes gut symptoms first when its level gets too high.3Learn the Heart. Digoxin Toxicity Topic Review Nausea, vomiting, belly pain and diarrhea are the most common warning signs of too much digoxin.4Learn the Heart. Digoxin Toxicity Topic Review5MedlinePlus. Digitalis toxicity: MedlinePlus Medical Encyclopedia Diarrhea and vomiting dry you out, and the resulting drop in kidney function can push the digoxin level higher still. Stomach upset while you are taking digoxin is a reason to call your doctor that day.
Digoxin levels can drift upward even when the dose hasn’t changed. It is cleared mostly by the kidneys, so anything that reduces kidney function lets it build up. Several other drugs, such as amiodarone, can raise digoxin levels, so a new prescription from any doctor is worth mentioning to the heart team. Low potassium, which diarrhea and water pills can cause, makes the heart more sensitive to digoxin even at a normal blood level. Older adults and people with small body size are more prone to toxicity, so doctors often use lower doses in them.
Digoxin toxicity can also cause a slow or irregular pulse, dizziness, fainting and unusual tiredness or confusion. Some people notice blurred or yellow-tinged vision or halos around lights. A slow or erratic pulse along with gut symptoms is a reason to seek urgent care rather than wait for a phone call back. Doctors confirm the problem with a blood test of the digoxin level, together with potassium and kidney function.
Olmesartan is a blood pressure pill sold as Benicar and in combination pills. It can damage the lining of the small bowel in a way that looks like celiac disease.6PubMed Central. Olmesartan Associated Enteropathy: A Rare Underdiagnosed Cause of Diarrhea and Weight Loss It causes long-lasting diarrhea and weight loss, often in people who have taken it for months or years.7PubMed Central. Olmesartan Associated Enteropathy: A Rare Underdiagnosed Cause of Diarrhea and Weight Loss8PubMed Central. Severe spruelike enteropathy associated with olmesartan Celiac blood tests come back negative, so it is easy to miss and people may go through many tests first.9PubMed Central. Olmesartan Associated Enteropathy: A Rare Underdiagnosed Cause of Diarrhea and Weight Loss If you take olmesartan and have unexplained ongoing diarrhea, ask your doctor whether the drug could be the cause, and don’t stop it on your own.
Other pills loosen stools too. Some rhythm drugs, such as quinidine, are known for diarrhea. Magnesium supplements and some antacids do the same, and antibiotics given for heart infections can upset the gut. Bring a full list of everything you take, including supplements.
To work out whether a medicine is responsible, note when the diarrhea started compared with any new pill or dose change. Never stop a heart drug without advice, because some cause rebound effects. For drugs like digoxin, your doctor may check blood levels.
When Diarrhea Signals an Emergency
Sudden severe belly pain that seems out of proportion to what a doctor finds can mean the bowel has lost its blood supply.10Cleveland Clinic Journal of Medicine. Mesenteric ischemia: Recognizing an uncommon disorder and distinguishing among its causes The pain is typically severe and constant, and the belly may feel surprisingly soft when pressed, which is why it can be underestimated. It tends to affect people with atrial fibrillation, heart failure, or recent heart surgery, and it can begin suddenly or after eating. Diarrhea, sometimes bloody, vomiting and urgency may come with it, and the condition can worsen within hours. Doctors confirm it with a CT scan using contrast dye, so say plainly in the emergency room that you have a heart condition and severe belly pain.
Heart infections can throw off clumps that weaken or block gut arteries, so belly pain, vomiting or diarrhea during or after one needs a scan.11PubMed. Aneurysms of the Superior Mesenteric Artery in Infective Endocarditis: A Case Series Bloody diarrhea with severe pain in someone with a weak heart or a heart-valve infection calls for the emergency room. People with artificial heart valves, previous valve infections, or certain congenital heart conditions are at higher risk. In such a person, fever lasting more than a few days, night sweats and unexplained tiredness deserve prompt evaluation even without gut symptoms. Gut symptoms in that setting can mean pieces of the infection have traveled, so mention the heart history right away.
Anaphylaxis, a severe allergic reaction, can cause vomiting, diarrhea, a dangerous drop in blood pressure and heart rhythm problems.12Johns Hopkins All Children’s Hospital. Anaphylaxis Diarrhea with hives, throat swelling or faintness after a food, sting or drug is an emergency. A sudden surge in the nerve that slows the heart can also bring cramping, nausea and an urge to pass stool just before fainting.13PubMed Central. Sleep Syncope: Treatment with a Permanent Pacemaker
Red flags at home include black or bloody stools, dizziness or fainting, and a very slow or racing pulse. Little urine or confusion suggests drying out. Chest pain or worsening breathlessness with the diarrhea also needs urgent care.
Dehydration is riskier with heart disease. Water pills already lower body fluid, and lost salts like potassium can trigger rhythm problems.
Diarrhea After Fontan Surgery for a Single Ventricle
The Fontan operation is used for children born with only one working pumping chamber.14PubMed. Protein-losing enteropathy and the Fontan operation It raises pressure in the veins, which can congest the liver and gut.15PubMed. Protein-losing enteropathy and the Fontan operation Some patients develop a condition where the gut leaks protein into the stool.16PubMed. Protein-losing enteropathy and the Fontan operation It can appear any time after surgery, even years later.17PubMed. Protein-Losing Enteropathy Following Fontan Palliation Signs include chronic diarrhea, belly pain, bloating, swelling and fluid in the belly or chest.18PubMed. Protein-Losing Enteropathy Following Fontan Palliation19PubMed. Protein-losing enteropathy and the Fontan operation In children it can slow growth.20PubMed. Protein-losing enteropathy and the Fontan operation Families should watch for puffy eyes or legs alongside loose stools, and for a child falling off their growth curve.
Tell the congenital heart team early, since blood protein tests can check for it.
Diagnosis begins with blood tests showing low albumin, a major blood protein, and often a stool sample for a protein that signals leakage from the gut. Doctors also check for other causes of low protein, such as kidney or liver problems, because the treatment differs. The heart team may do a catheter study or imaging to look at pressures in the Fontan circulation and for any fixable blockage.
Treatment depends on the cause, and when a narrowing or other problem in the circulation can be fixed, the protein-losing gut may improve. Doctors may recommend a low-fat diet with certain fats that are absorbed differently, and sometimes give budesonide or heart medicines that lower vein pressure. In severe cases, some patients are evaluated for more advanced options, which is why early referral to a specialist center matters.
Conditions That Affect Both the Heart and the Bowel
Some slow-growing tumors release large amounts of serotonin, causing flushing and diarrhea.21PubMed. Carcinoid heart disease. Correlation of high serotonin levels with valvular abnormalities detected by cardiac catheterization and echocardiography Over time serotonin scars the valves on the right side of the heart.22PubMed Central. Carcinoid syndrome revealed by chronic diarrhea and isolated severe tricuspid regurgitation People with this heart damage are nearly three times as likely to have flushing and diarrhea.23PubMed. Carcinoid heart disease. Correlation of high serotonin levels with valvular abnormalities detected by cardiac catheterization and echocardiography A 24-hour urine test called 5-HIAA measures the serotonin excess, and values above about 300 µmol a day are linked to valve damage.24PubMed Central. Carcinoid syndrome revealed by chronic diarrhea and isolated severe tricuspid regurgitation
The tumors usually start in the small bowel or appendix, and the syndrome typically appears only after they spread to the liver, which lets serotonin reach the bloodstream. Doctors order the urine serotonin test together with imaging to find the tumors, and a heart ultrasound looks at the valves. Medicines like octreotide ease flushing and diarrhea while treatment aims to control the tumor. Damaged valves can sometimes be replaced when heart failure develops, so finding this early matters.
Thyroid storm is a rare, life-threatening flare of an overactive thyroid.25PubMed. High risk and low prevalence diseases: Thyroid storm It causes fever, a racing heart, heart failure, vomiting and diarrhea.26PubMed. High risk and low prevalence diseases: Thyroid storm27PubMed Central. Approach to the patient with thyroid storm It usually follows a trigger such as infection, surgery, or stopping thyroid medicine. Body temperature climbs, the heartbeat can become dangerously fast and irregular, and agitation can progress to confusion or coma. Diarrhea with a pounding fast heartbeat, fever and confusion needs emergency care. Treatment happens in hospital with medicines to block thyroid hormone and slow the heart, plus cooling and fluids.
In amyloidosis, misfolded proteins build up in organs including the heart and the bowel lining, causing diarrhea and poor absorption.28PubMed Central. Gastrointestinal (GI) Amyloidosis Presenting As Chronic Diarrhea: A Diagnostic Dilemma Chagas disease, a parasitic infection common in Latin America, damages the heart and gut nerves and can cause chronic diarrhea from bacterial overgrowth.29PubMed Central. The Chronic Gastrointestinal Manifestations of Chagas Disease Diabetes can damage the nerves controlling both heart rate and the gut, and faster passage through the small bowel goes with more diarrhea.30PubMed Central. Diabetic gastroenteropathy: Associations between gastrointestinal symptoms, motility, and extraintestinal autonomic measures In people with this nerve damage, most have measurable gut movement problems, some too fast and many too slow.31PubMed Central. Quantitative gastrointestinal function and corresponding symptom profiles in autonomic neuropathy
Managing Diarrhea When You Have Heart Disease
Stomach bugs and food poisoning remain the usual causes, and short bouts that clear in a day or two are rarely heart-related. Diarrhea lasting over two weeks deserves a full check-up.
Oral rehydration drinks replace both water and salts better than plain water. People on fluid limits for heart failure should ask how much they can safely drink. Doctors sometimes pause water pills or certain blood pressure drugs during severe diarrhea to prevent kidney injury, so keep a sick-day plan from your doctor for which pills to hold. It typically lists which medicines to pause during vomiting or diarrhea, such as water pills, ACE inhibitors, ARBs and some diabetes drugs, and when to restart them. It sets a trigger, such as symptoms lasting more than a day, for when to start the plan and when to call. It should also say which medicines must not be skipped, such as many rhythm and blood-thinning drugs, so ask for a written copy.
Sports drinks and juice are usually too sugary and low in salt, and sugary drinks can worsen diarrhea, so oral rehydration drinks are the better choice. For people on a low-sodium diet, the salt in rehydration drinks is intended for the short term, so ask the doctor how to balance it with heart-failure advice. Small frequent sips are better tolerated than large gulps when nausea is present.
Common anti-diarrhea medicines are fine for many people, but ask a pharmacist first if you take rhythm drugs. Loperamide is widely used, but at doses well above the label it can cause dangerous heart rhythm problems, so stay within the package limit. It should not be used when there is high fever or blood in the stool, because it can hide or worsen a serious infection. Bismuth products can interact with some medicines and contain salicylate, so check with a pharmacist if you take a blood thinner.
When you call your doctor, say how long the diarrhea has lasted and how many stools a day you have. Mention any new medicines or dose changes, your daily weights and urine output, and any blood, fever, or dizziness.