If you’re struggling to have a bowel movement, the most likely culprits are not drinking enough water, not eating enough fiber, or spending too much time sitting still. But constipation has a surprisingly long list of possible causes, from medications to muscle coordination problems to thyroid issues. Normal bowel frequency ranges from three times a day to three times a week, so if you’re going less than three times a week, or straining through more than a quarter of your bowel movements, something is off.
You’re Probably Not Eating or Drinking Enough of the Right Things
The most common reason people can’t poop is a combination of too little fiber and too little fluid. Fiber adds bulk and softness to stool, giving your intestines something to grip and push along. Without it, stool moves slowly and dries out. Most adults fall well short of the recommended daily intake: 25 grams for women under 50 (21 grams over 50) and 38 grams for men under 50 (30 grams over 50). For reference, a cup of cooked broccoli has about 5 grams. If your diet leans toward white bread, cheese, and processed foods, you’re likely getting half of what you need.
Water matters just as much. When your body doesn’t get enough fluid, your colon compensates by pulling extra water out of the stool to keep the rest of your body hydrated. That leaves you with dry, hard stool that’s painful and difficult to pass. A large study using U.S. national health data found that higher fluid intake was associated with a 19% lower risk of constipation, and the relationship held even after accounting for diet, age, and other factors. Fluid also helps trigger the wave-like contractions that move stool through your intestines. Coffee, tea, and water-rich foods all count toward your total intake.
Your Medications Could Be Slowing Things Down
Constipation is one of the most reported side effects across dozens of common medications. Opioid painkillers are the most well-known offenders because they directly slow the muscles in your intestinal wall, but they’re far from the only ones. Antidepressants (particularly older types and some newer ones like duloxetine and pregabalin), heartburn drugs that contain calcium or aluminum, iron supplements, blood pressure medications, and allergy pills that contain antihistamines can all make it harder to go.
Some less obvious medications also cause problems. Weight-loss drugs like orlistat and semaglutide, smoking cessation aids like varenicline, and even some biologic drugs used for autoimmune conditions have constipation as a frequently reported side effect. If your trouble started around the same time you began a new medication, that connection is worth investigating. Stopping or switching a drug on your own isn’t safe, but knowing that your medication could be the cause helps you have the right conversation with your doctor.
Your Muscles Might Not Be Working Together
Having a bowel movement requires surprisingly precise coordination. Your abdominal muscles need to push down while the muscles around your anus relax and open. When these two actions don’t sync up, you can strain as hard as you want and nothing comes out. This condition, called dyssynergic defecation, is more common than most people realize, and it’s a learned behavior rather than a structural problem.
There are several ways the coordination can break down. Some people generate plenty of pushing force but their anal muscles clench tighter instead of relaxing. Others can’t produce enough push in the first place. Some have both problems at once. The result is the same: you feel the urge, you sit on the toilet, you strain, and the stool simply won’t move. It can feel like pushing against a closed door.
The good news is that because this is a coordination issue, it responds well to a type of physical therapy called biofeedback training. A therapist uses sensors to show you in real time what your pelvic floor muscles are doing, then coaches you to push and relax in the right pattern. Most people see significant improvement within a few sessions.
Your Thyroid or Electrolytes May Be Involved
Your thyroid gland sets the pace for many body functions, including how fast your intestines contract. When thyroid hormone levels drop too low (hypothyroidism), the muscles lining your colon contract with less force and less frequency. Stool sits in the colon longer, more water gets absorbed, and the result is infrequent, hard, difficult-to-pass bowel movements. In studies measuring colonic pressure, people with hypothyroidism showed noticeably weaker contractions than people with normal thyroid function.
The constipation caused by low thyroid typically improves once hormone levels are corrected with replacement therapy. If your constipation came on gradually and you also feel unusually tired, cold, or sluggish, or if you’ve noticed weight gain, dry skin, or thinning hair, a simple blood test can check your thyroid levels. Electrolyte imbalances, particularly low potassium or high calcium, can also weaken intestinal contractions and should be ruled out if constipation is persistent and unexplained.
Lifestyle Habits That Make It Worse
Sitting at a desk all day slows your gut. Physical movement stimulates the rhythmic contractions that push stool through the colon, so a sedentary routine can leave things stalled. Even a daily 20-minute walk makes a measurable difference for many people.
Ignoring the urge is another common habit that backfires. When you feel the need to go but hold it because you’re busy or not near a comfortable bathroom, your rectum stretches to accommodate the stool. Over time, the stretch receptors become less sensitive, and the urge fades. The stool stays in the colon, loses more water, and becomes harder to pass later. Responding to the urge promptly, especially in the morning or after meals when your colon is most active, helps keep things on schedule.
Stress also plays a role. Your gut has its own nervous system, and it responds to anxiety by either speeding up or slowing down. For many people, chronic stress puts the brakes on motility. Poor sleep compounds this by disrupting the hormonal signals that regulate digestion overnight.
What You Can Try at Home
Start with the basics: increase your fiber gradually (adding too much at once causes gas and bloating), drink more water throughout the day, and move your body daily. If those changes don’t help after a week or two, over-the-counter options work through two different mechanisms.
Osmotic laxatives, like polyethylene glycol (MiraLAX) or milk of magnesia, draw water into the intestine. This softens the stool and makes it easier to pass. They’re generally gentle and safe for regular use. Stimulant laxatives, like senna or bisacodyl, take a more active approach by triggering the muscles in your intestinal wall to contract while also preventing the colon from reabsorbing water. Stimulants work faster but are better suited for occasional use rather than daily reliance.
Positioning matters too. Sitting on a standard toilet puts your body at an angle that partially kinks the rectum. Placing a small stool under your feet to raise your knees above your hips straightens that angle and can make evacuation noticeably easier.
Signs That Something More Serious Is Going On
Most constipation is uncomfortable but not dangerous. However, certain symptoms alongside constipation need prompt medical attention: blood in your stool, unexplained weight loss, vomiting, or severe abdominal pain with major bloating. Going a prolonged stretch without any bowel movement at all, combined with increasing pain and bloating, can signal a bowel obstruction, which is a medical emergency. A sudden, lasting change in bowel habits after age 50, especially with blood or weight loss, warrants screening to rule out colorectal issues.