Hemorrhoids develop when the cushions of tissue lining your anal canal become swollen and inflamed, usually from too much pressure on the veins in your lower rectum. More than 20% of the population deals with hemorrhoids at some point, making them one of the most common gastrointestinal problems. In the United States alone, they account for roughly 3.3 million medical visits per year. The good news: once you understand what causes that pressure buildup, most of the risk factors are things you can control.
What Actually Happens Inside Your Body
Hemorrhoids aren’t varicose veins, though they’re often described that way. They’re clusters of blood vessels, smooth muscle, and connective tissue that everyone has naturally. These cushions help with continence and sit along the lining of the anal canal. Problems start when pressure builds up and interferes with normal blood flow, causing those cushions to swell, stretch, and sometimes slip out of position.
When you strain on the toilet or sit there for extended periods, blood pools in the vessels of the anal canal. Think of it like a tourniquet effect: the pressure prevents blood from draining back toward the heart, so the tissue engorges. Over time, the connective tissue supporting these cushions weakens, which is why hemorrhoids become more common as you age. If they eventually bleed, the blood is typically bright red because the bleeding comes from arterial vessels, not veins.
Straining and Constipation
The single biggest driver of hemorrhoids is straining during bowel movements. When you bear down hard to pass stool, you dramatically increase the pressure inside your abdomen. That force pushes directly on the blood vessels in your rectum and anus. Do this repeatedly over weeks and months, and the tissue swells and stays swollen.
Constipation is usually what makes people strain in the first place. Hard, dry stools are difficult to pass without effort. A low-fiber diet is the most common cause of this cycle. Without enough fiber, your stools are smaller and firmer, requiring more force to move through. Fiber softens and bulks up stool so it passes with minimal effort, which is why increasing fiber intake is the first recommendation for both preventing and managing hemorrhoids.
Sitting Too Long on the Toilet
Spending extra time on the toilet is a surprisingly significant factor. A study comparing smartphone users to non-users found that 37.3% of people who used their phones on the toilet spent more than 5 minutes per trip, compared to just 7.1% of those who didn’t bring a phone. That extended sitting time was linked to higher rates of hemorrhoids.
The reason is mechanical. When you sit on a toilet, the shape of the seat puts direct pressure on the tissue around your anus while leaving the anal canal unsupported. This creates that tourniquet effect, trapping blood in the hemorrhoidal cushions. Reading, scrolling, or just sitting there waiting adds minutes of unnecessary pressure. The practical fix is simple: if nothing is happening after a few minutes, get up and try again later.
Pregnancy
Hemorrhoids are extremely common during pregnancy, and several factors converge to make them almost unavoidable for many women. Rising progesterone levels relax the walls of blood vessels throughout the body, including those in the rectal area. Relaxed vessel walls are more prone to swelling and stretching under pressure.
At the same time, total blood volume increases significantly to support the growing baby. More blood flowing through the pelvic region means more pressure on the veins that drain the anal canal. As the uterus grows, it also physically compresses those veins, further slowing blood return. Add in the constipation that many pregnant women experience from hormonal changes and iron supplements, and the conditions for hemorrhoid development are almost perfect. Most pregnancy-related hemorrhoids improve after delivery once these pressures ease.
Heavy Lifting and Exercise
Lifting heavy weights can cause or worsen hemorrhoids if your technique involves straining or breath-holding. When you hold your breath during a heavy lift, pressure builds in your abdominal cavity. That pressure transfers to the blood vessels in your rectum and anus, forcing them to swell. Squats with heavy loads are particularly risky because the weight on your spine compounds the abdominal pressure.
This doesn’t mean you need to avoid the gym. The key is proper breathing technique: exhaling during the exertion phase rather than holding your breath. Lighter weights with more repetitions create far less abdominal pressure than maximal lifts. High-intensity programs that combine jumping, squatting, and heavy lifting in rapid succession can be especially problematic. Rowing machines are a quieter culprit too, combining prolonged sitting with repeated forceful pushing and pulling.
Other Contributing Factors
Aging plays a clear role. The connective tissue that anchors hemorrhoidal cushions in place weakens over time, making it easier for swollen tissue to prolapse, or slip downward out of the anal canal. This is why hemorrhoids are more common in people over 40 and increasingly so with each decade.
Chronic diarrhea can be just as damaging as constipation. Frequent loose stools irritate the anal lining, and the repeated urgency and straining that come with diarrhea put similar pressure on the hemorrhoidal tissue. Obesity adds sustained pressure to the pelvic floor throughout the day, not just during bowel movements. A sedentary lifestyle compounds this by reducing the muscle tone that supports healthy blood flow in the pelvic region.
Abnormally high tension in the internal sphincter muscle, the ring of muscle that controls the anal opening, can also restrict blood flow and contribute to swelling. Some people naturally have higher resting sphincter pressure, which may partly explain why hemorrhoids seem to run in families.
What You Can Do to Lower Your Risk
Most hemorrhoid prevention comes down to reducing the pressure on your lower rectum. Eating 25 to 30 grams of fiber daily through fruits, vegetables, whole grains, and legumes keeps stools soft enough to pass without straining. Drinking plenty of water is essential for fiber to work properly. Without adequate hydration, extra fiber can actually make constipation worse.
Go to the bathroom when you feel the urge rather than waiting. Delaying bowel movements allows stool to dry out and harden in the rectum, making it harder to pass later. Once you’re on the toilet, limit your time. If you need to strain significantly, that’s a sign your stool is too hard or your body isn’t quite ready, and either way, pushing through it does more harm than good.
Regular physical activity helps keep your digestive system moving and supports healthy circulation in the pelvic area. Walking, swimming, and moderate exercise are all beneficial. If you lift weights, focus on breathing technique and avoid loads that force you to hold your breath. Standing periodically throughout the day also helps if you have a desk job, since prolonged sitting in any context increases pressure on the anal area.