What Causes Hemorrhoids? Every Risk Factor Explained
Hemorrhoids don't happen randomly. They develop when sustained or repeated pressure causes the veins in the lower rectum and anal canal to stretch, swell, and bulge beyond their normal capacity. That pressure can come from a single acute event — one episode of severe straining — or from years of chronic factors that gradually weaken the tissue until it gives way.
Understanding the specific cause of your hemorrhoids isn't just academic. Each cause points directly to a prevention strategy, and addressing the right one is the difference between a hemorrhoid that resolves and one that keeps coming back.
This guide covers every significant cause and risk factor — with the mechanism behind each one, the evidence supporting it, and what to actually do about it.
The Core Mechanism: How Any Hemorrhoid Forms
Before the specific causes, it helps to understand the common pathway they all share.
The anal canal contains three cushions of vascular tissue — the hemorrhoidal plexus — that help seal the anal opening and contribute to continence. These cushions are normal anatomy; everyone has them. They become "hemorrhoids" only when they swell, prolapse, or cause symptoms.
The swelling is caused by increased pressure in the hemorrhoidal veins that exceeds their ability to drain blood back into the circulation. When outflow is restricted and inflow continues, the veins engorge. If this happens repeatedly — or for long enough — the connective tissue that anchors the cushions in place stretches and weakens, allowing the tissue to slide downward (prolapse) or bulge outward.
Every cause of hemorrhoids works through this same pathway: it either increases pressure in the hemorrhoidal veins, restricts drainage, weakens the supporting connective tissue, or some combination of all three.
Cause 1: Straining During Bowel Movements
The single most common cause — and the one most directly actionable.
The mechanism
When you bear down to pass a stool, intra-abdominal pressure spikes dramatically. This pressure transmits directly to the veins of the rectum and anal canal, forcing blood into the hemorrhoidal plexus faster than it can drain. In short, controlled episodes this is normal. But when straining is prolonged — more than a minute or two — or repeated multiple times per day, the sustained pressure causes the hemorrhoidal veins to engorge and, over time, the supporting tissue to stretch.
Straining also engages the Valsalva maneuver (bearing down against a closed glottis), which briefly but significantly raises venous pressure throughout the lower body, including the rectal veins.
Why hard stools make it worse
The physics are straightforward: a hard, dry stool requires more force to pass than a soft one. More force means more prolonged Valsalva, more sustained pressure in the rectal veins, and more trauma to hemorrhoidal tissue as the hard mass passes over it. This is why the relationship between constipation and hemorrhoids is so direct.
What to do about it
- Target soft, formed stools that pass with minimal effort — this is the goal of fiber and hydration
- If a bowel movement isn't coming easily within 2–3 minutes of trying, get up and try later — the urge will return
- Limit toilet time to under 5 minutes; phones and reading extend sitting time and unconsciously encourage straining
- Use a footstool (Squatty Potty or equivalent) to approximate the squatting position — this straightens the anorectal angle and reduces the effort required to pass stool
Cause 2: Low Dietary Fiber
Directly linked to Cause 1, but worth separating because it's the most modifiable root cause.
The mechanism
Dietary fiber absorbs water in the colon, adds bulk to stool, and softens it. The result is a stool that passes easily without straining. Without adequate fiber, stool is compact, dry, and hard — requiring significantly more effort to pass. The average Western diet contains 10–15g of fiber per day; the recommended amount is 25–35g.
Soluble fiber (oats, psyllium, fruits, legumes) forms a gel in the colon that softens stool. Insoluble fiber (whole grains, vegetables) adds bulk that stimulates peristalsis and speeds transit. Both are useful; psyllium husk supplements provide primarily soluble fiber and are the most studied for hemorrhoid prevention and symptom reduction.
The evidence
Multiple randomized controlled trials show that fiber supplementation reduces hemorrhoid bleeding and the risk of recurrent symptoms by roughly 50%. It's one of the few interventions with consistent evidence across studies.
What to do about it
- Aim for 25–35g of dietary fiber daily from food (fruits, vegetables, legumes, whole grains) or supplements
- Psyllium husk (Metamucil, Konsyl) is the most studied supplement — start with one dose daily and increase gradually to avoid gas and bloating
- Increase fiber gradually over 2–3 weeks — jumping from 10g to 35g immediately causes significant bloating
- Drink more water alongside fiber increases — fiber absorbs water, and without adequate hydration it can paradoxically worsen constipation
Cause 3: Dehydration and Insufficient Fluid Intake
The mechanism
The colon absorbs water from stool as it passes through. When the body is dehydrated, it extracts more water from stool to compensate — leaving it drier and harder. Even mild, chronic dehydration (below 6–8 glasses of water daily) contributes to consistently harder stools and the straining that follows.
Caffeine and alcohol both have diuretic effects — they increase urine output and can contribute to relative dehydration if not compensated with water intake. This doesn't mean avoiding coffee causes hemorrhoids, but it does mean that a diet heavy in caffeine or alcohol without adequate water intake is a contributing factor.
What to do about it
- 8 glasses (2 liters) of water daily is the standard recommendation; more if physically active or in a hot climate
- For every cup of coffee or alcoholic drink, add an extra glass of water
- Pale yellow urine is the simplest indicator of adequate hydration
Cause 4: Chronic Constipation
Constipation deserves its own section separate from "low fiber" because it has multiple causes — and because chronic constipation is the single most significant modifiable risk factor for hemorrhoid development and recurrence.
The mechanism
Constipation means infrequent bowel movements (fewer than 3 per week) or consistently difficult passage of hard stool. Both lead directly to the straining described above. But chronic constipation adds an additional factor: the stool sits in the rectum for longer periods, and the weight and pressure of retained stool against the rectal wall increases pressure in the surrounding hemorrhoidal veins even when not actively straining.
Common causes of constipation beyond low fiber
- Iron supplements — one of the most common causes of constipation in women (particularly during pregnancy and postpartum)
- Opioid pain medications — cause significant constipation in most users
- Certain antidepressants and antipsychotics — slow GI motility
- Hypothyroidism — slows the entire GI tract
- Irritable bowel syndrome (IBS-C) — chronic constipation pattern
- Ignoring the urge to defecate — repeatedly suppressing the urge leads to progressive stool drying and harder-to-pass stools
- Sedentary lifestyle — physical activity stimulates bowel motility
What to do about it
- Address the underlying cause of constipation, not just the symptom
- If on iron supplements: ask your doctor about slow-release formulations (better tolerated) or liquid iron (less constipating); vitamin C taken with iron improves absorption and allows lower doses
- If on opioids: prophylactic stool softeners (docusate sodium) and osmotic laxatives (polyethylene glycol) should be started simultaneously — opioid-induced constipation rarely resolves without intervention
- Never suppress the urge to defecate — respond when the urge is present
Cause 5: Prolonged Sitting — Especially on the Toilet
The mechanism
Extended sitting increases pressure in the perianal veins in two ways. First, the seated position puts direct pressure on the perineum, partially compressing the venous drainage from the anal area. Second — and more specifically for toilet sitting — the toilet seat creates a "ring" of support around the buttocks while the anal area hangs unsupported in the opening. This unsupported position allows the hemorrhoidal tissue to engorge without the counter-pressure that would exist when standing or squatting.
Studies show that people who read or use their phones on the toilet sit significantly longer than those who don't — and longer toilet sitting is associated with higher rates of hemorrhoids.
Beyond the toilet
Office workers, drivers, and anyone who sits for 6+ hours daily face increased risk from general prolonged sitting, even away from the toilet. The continuous compression of perianal veins reduces circulation and contributes to venous engorgement over time.
What to do about it
- Limit toilet sitting to the time actually needed — under 5 minutes is the target; leave the phone elsewhere
- For sedentary work: stand up and walk for 5 minutes every hour; even brief movement restores circulation
- A standing desk or alternating between sitting and standing reduces cumulative daily pressure
- Sitting on softer, wider surfaces distributes pressure better than hard chairs
Cause 6: Pregnancy
One of the most common times for hemorrhoids to first appear — affecting up to 85% of women in the third trimester to some degree.
The mechanism
Pregnancy contributes through three simultaneous pathways:
Mechanical compression: The growing uterus presses directly on the inferior vena cava (the large vein returning blood from the lower body to the heart) and on the pelvic veins. This compression reduces venous return from the lower body, increasing backpressure in the hemorrhoidal plexus. The effect increases progressively as the uterus grows, peaking in the third trimester.
Hormonal effects: Progesterone, which rises throughout pregnancy, relaxes smooth muscle throughout the body — including the walls of blood vessels. This makes the hemorrhoidal veins more distensible and less able to maintain normal tone, contributing to engorgement even without external pressure.
Constipation: Progesterone also slows GI motility. Iron supplements taken during pregnancy compound this. The result is that most pregnant women experience some degree of constipation — which adds the straining mechanism on top of the mechanical and hormonal contributions.
Labor: The intense bearing down during the second stage of labor is one of the most acute hemorrhoid triggers there is — hours of sustained Valsalva against maximum resistance.
What to do about it
- Fiber and hydration are safe and effective throughout pregnancy — start early, don't wait for symptoms
- Sitz baths are safe throughout pregnancy; avoid very hot water
- Side-lying positions (left lateral) improve venous return from the lower body and reduce IVC compression — relevant both for sleeping and for positioning during prolonged rest
- Most pregnancy-related hemorrhoids improve significantly within 6–8 weeks postpartum as uterine pressure resolves
Cause 7: Heavy Lifting and High-Intensity Exercise
The mechanism
Heavy lifting — particularly compound lifts like squats, deadlifts, and overhead presses — produces significant spikes in intra-abdominal pressure, especially when performed with breath held (Valsalva maneuver). This is identical in mechanism to straining on the toilet: a rapid, intense increase in pressure transmitted to the rectal and hemorrhoidal veins.
A single heavy lifting session rarely causes hemorrhoids. But repeated high-intensity training without adequate recovery, fiber intake, and hydration — especially in people who already have hemorrhoidal tissue changes — can trigger or worsen them.
High-intensity activities that also increase intra-abdominal pressure: rowing, cycling (also adds direct pressure on the perineum), gymnastics, CrossFit-style training.
What to do about it
- Exhale during the concentric (exertion) phase of lifts — reduces sustained Valsalva
- Ensure high fiber and hydration to counter the constipating effect of protein-heavy diets common in weightlifters
- During an active hemorrhoid flare: avoid heavy lifting until resolved — walking, swimming, and yoga are appropriate
- Cycling during a flare: use a padded, wide seat or take a break — the perineal pressure worsens external hemorrhoids specifically
Cause 8: Chronic Diarrhea
Less commonly associated with hemorrhoids than constipation — but a significant cause, particularly for external hemorrhoids.
The mechanism
Frequent loose bowel movements (more than 3 per day chronically) cause mechanical irritation and inflammation of the anal tissue through sheer volume of contact. The repeated passage of liquid stool, often acidic, inflames the perianal skin and the hemorrhoidal tissue. The physical act of multiple daily bowel movements also strains the anal sphincter and surrounding vasculature repeatedly.
Chronic diarrhea from IBD (Crohn's disease, ulcerative colitis), IBS-D, or infectious causes all carry increased hemorrhoid risk through this mechanism.
What to do about it
- Treat the underlying cause of chronic diarrhea — hemorrhoids from IBD won't fully resolve until the IBD is managed
- Protect the perianal skin with a zinc oxide barrier after each bowel movement during diarrhea episodes
- Gentle cleaning — a peri bottle with warm water rather than aggressive wiping
- Witch hazel wipes (alcohol-free) reduce inflammation between bowel movements
Cause 9: Obesity
The mechanism
Excess body weight increases resting intra-abdominal pressure — the baseline pressure inside the abdominal cavity even when not straining. This increased baseline means that everyday activities — standing, walking, bending — create more pressure on the hemorrhoidal veins than in people with healthy weight. It also means there's less reserve before straining tips the pressure into the range that causes hemorrhoidal engorgement.
Additionally, obesity is associated with higher rates of constipation (reduced physical activity, dietary patterns) and type 2 diabetes (autonomic neuropathy can affect GI motility), both of which contribute indirectly.
What to do about it
- Weight loss, even modest (5–10% of body weight), reduces intra-abdominal pressure meaningfully
- The dietary changes that support weight loss (more fiber, more vegetables, less processed food) directly address hemorrhoid risk through the fiber mechanism simultaneously
Cause 10: Age and Connective Tissue Weakening
The mechanism
The hemorrhoidal cushions are held in place by connective tissue — a network of collagen and elastin fibers that provide structural support. With age, this tissue gradually loses elasticity and tensile strength. The same process that causes skin to sag and joints to become less stable affects the supportive tissue of the anal canal.
This weakening means that the hemorrhoidal cushions can slide downward (prolapse) more easily under pressure, and that the veins themselves become more distensible and slower to return to normal caliber after engorgement. This is why hemorrhoids become significantly more common after age 45 — not because older adults suddenly strain more, but because the tissue holding everything in place becomes less resilient.
What to do about it
- Age-related connective tissue changes can't be reversed, but the load on that tissue can be reduced through fiber, hydration, and avoiding straining — meaning the same lifestyle changes are relevant at any age, and more important with age
- Pelvic floor exercises (Kegel exercises) maintain tone in the muscles that support the pelvic floor, which indirectly supports the hemorrhoidal tissue
Cause 11: Genetics
The mechanism
The tendency to develop hemorrhoids runs in families — and the mechanism is primarily genetic variation in the structural properties of veins and connective tissue. People with naturally more distensible vein walls, or with connective tissue that is less resistant to stretching, develop hemorrhoids more easily under the same amount of pressure as people with stiffer tissue.
This is why some people eat low-fiber diets for decades without ever developing hemorrhoids, while others eat high-fiber and still struggle with recurrence — genetics sets the baseline susceptibility.
What to do about it
- You can't change your genetics, but you can dramatically reduce the load on whatever hemorrhoidal tissue you have
- If hemorrhoids run strongly in your family, be proactive — don't wait for symptoms to start the high-fiber, high-hydration lifestyle
Cause 12: Low-Fiber, High-Fat Western Diet (Beyond Just Fiber)
The hemorrhoid rate in populations eating traditional high-fiber diets (rural Africa, rural Asia) is dramatically lower than in populations eating Western diets — and the difference goes beyond just fiber content.
High-fat, low-fiber diets slow colonic transit time, alter the gut microbiome in ways that affect stool consistency, and tend to be lower in the phytonutrients that maintain vascular integrity. The cumulative effect of all these factors compounds the direct fiber deficit.
Spicy food — a common myth — does not cause hemorrhoids. It can irritate existing hemorrhoidal tissue and worsen symptoms during a flare, but there's no evidence it causes hemorrhoid formation.
Cause 13: Portal Hypertension (Less Common)
In people with liver disease (cirrhosis, hepatitis), pressure in the portal venous system — which drains the intestines — can become elevated. This increased portal pressure backs up into the hemorrhoidal veins, causing them to engorge independently of any straining or lifestyle factors.
Hemorrhoids from portal hypertension are different from typical hemorrhoids: they tend to bleed more significantly, respond less well to standard treatments, and require management of the underlying liver condition. If you have known liver disease and develop significant rectal bleeding, this distinction matters for treatment.
How Risk Factors Interact
No single cause operates in isolation. The hemorrhoid risk is cumulative — and this is why some people seem to get hemorrhoids "easily" while others don't despite similar habits.
A 50-year-old office worker (age + prolonged sitting) who eats a low-fiber diet (constipation risk) and is overweight (increased intra-abdominal pressure) faces the compounding of three or four independent risk factors simultaneously. Any one of them might not be sufficient alone; together they push well past the threshold.
This also explains why addressing multiple factors simultaneously is more effective than fixing just one. Adding fiber alone while continuing to strain, sit for hours, and be dehydrated produces modest improvement. Addressing fiber, hydration, toilet habits, and sitting together can eliminate most hemorrhoid episodes.
The Causes You Can't Change vs The Ones You Can
| Modifiable | Non-modifiable |
|---|---|
| Dietary fiber intake | Age |
| Hydration | Genetics |
| Toilet habits and time | Pregnancy (the pregnancy itself) |
| Physical activity | Portal hypertension from liver disease |
| Body weight | |
| Medication side effects (with doctor) | |
| Constipation treatment | |
| Lifting technique |
The non-modifiable causes are relatively few. The vast majority of hemorrhoid risk is modifiable — which means that for most people, hemorrhoids are largely preventable and highly treatable through lifestyle.
For a complete prevention strategy, see How to Prevent Hemorrhoids
FAQs
What is the most common cause of hemorrhoids?
Straining during bowel movements from constipation — itself usually caused by low dietary fiber and insufficient hydration. Addressing these two factors (fiber to 25–35g daily, water to 8+ glasses daily) is the most effective single intervention for both prevention and reducing recurrence.
Can stress cause hemorrhoids?
Indirectly, yes. Stress doesn't directly affect the hemorrhoidal veins, but it commonly causes constipation or diarrhea through the gut-brain axis — both of which are direct causes. Stress also causes generalized muscle tension including in the pelvic floor, which can increase baseline anal pressure. Managing stress reduces hemorrhoid flares in people whose GI symptoms are stress-responsive.
Can sitting too long cause hemorrhoids?
Yes — particularly sitting on the toilet, which leaves the anal tissue unsupported and under sustained pressure. General prolonged sitting (office work, long drives) also increases risk by compressing perianal veins and reducing circulation. Limiting toilet time to under 5 minutes and taking regular breaks from sitting are both evidence-supported recommendations.
Do hemorrhoids run in families?
Yes — genetics influences the distensibility of vein walls and the strength of the connective tissue that supports the hemorrhoidal cushions. If one or both parents had hemorrhoids, your baseline susceptibility is higher. This doesn't make hemorrhoids inevitable, but it does mean the lifestyle factors (fiber, hydration, not straining) matter more, not less.
Can diet cause hemorrhoids?
A low-fiber diet is the dietary cause most directly linked to hemorrhoids — through hard stools and constipation. But high-fat, low-vegetable Western diets also slow colonic transit, alter gut microbiome, and reduce vascular integrity through multiple mechanisms. The good news: dietary changes are among the most effective interventions, and improvement is typically seen within days of increasing fiber.
Can alcohol cause hemorrhoids?
Alcohol is a diuretic — it increases urine output and contributes to dehydration, which hardens stools and increases straining risk. Heavy alcohol use also affects liver function, which can contribute to portal hypertension and associated hemorrhoidal engorgement in severe cases. Moderate alcohol use doesn't directly cause hemorrhoids, but dehydration from drinking without adequate water intake is a contributing factor.
Why do hemorrhoids come back after they heal?
Because the cause hasn't been addressed. A hemorrhoid that heals while the underlying constipation, straining, low fiber intake, or prolonged sitting continues will recur — often repeatedly. Permanent lifestyle changes (sustained high fiber, hydration, toilet habit modification) are the only reliable way to prevent recurrence. About 50% of people have a recurrence within 5 years without addressing root causes; with lifestyle changes, that rate drops significantly.
Can hemorrhoids be caused by not wiping properly?
Poor wiping technique doesn't cause hemorrhoids — but it can worsen existing ones. Aggressive wiping with dry toilet paper traumatizes already-inflamed hemorrhoidal tissue, delays healing, and can cause bleeding and skin breakdown. Using moist, unscented wipes or a bidet for cleaning, and patting dry rather than rubbing, reduces this irritation without causing hemorrhoids in the first place.
Key Takeaways
- All hemorrhoids share the same final pathway: increased pressure in the hemorrhoidal veins exceeding the tissue's ability to drain and recover.
- The most common and most modifiable cause: constipation from low dietary fiber leading to straining. Fixing this one factor has the largest impact.
- Prolonged toilet sitting, pregnancy, heavy lifting, obesity, chronic diarrhea, and age are all independent risk factors that compound each other.
- Genetics and age set your baseline susceptibility — they can't be changed, but the load on the tissue absolutely can.
- Most causes are fully modifiable — hemorrhoids are, for most people, largely preventable with sustained lifestyle changes.
- Recurrence is common when root causes aren't addressed. The hemorrhoid healing is not the finish line — the lifestyle change is.
🩺 Reviewed by: Hemorrhoid Care Hub Medical Review Team 📅 Last reviewed: October 1, 2025 ℹ️ Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a healthcare provider for diagnosis and treatment.