Constipation Causes, Symptoms & Prevention Techniques

Constipation is one of the most common reasons patients bring up something to their doctor that they’ve been quietly managing on their own for months. It is uncomfortable, disruptive, and — when chronic — genuinely affects quality of life, energy, mood, and sleep. And yet it carries enough social awkwardness that many people either push through it or reach for whatever is on the pharmacy shelf without really understanding what’s happening or why.

Let’s fix that.

Constipation affects an estimated 10–15% of the global population and is significantly more common in women than men — at roughly twice the rate. It is also more prevalent in non-White populations, in adults over 65, and in people with sedentary lifestyles or low-fiber diets, according to the 2024 American Society of Colon and Rectal Surgeons (ASCRS) evaluation and management guidelines. The fact that it is common does not make it something you should simply normalize. Persistent constipation is a clinical signal — and understanding it is the first step to addressing it effectively.

What Is Constipation — Clinically Defined

The Rome IV criteria — the standard clinical definition used by gastroenterologists — define constipation as the presence of two or more of the following symptoms for at least 3 months:

Fewer than 3 spontaneous bowel movements per week
Straining during more than 25% of defecations
Lumpy or hard stools (Bristol Stool Scale type 1 or 2) during more than 25% of defecations
Sensation of incomplete evacuation during more than 25% of defecations
Sensation of anorectal blockage during more than 25% of defecations
Need for manual maneuvers (pressing around the rectum) to facilitate defecation

Most people think of constipation only as infrequent bowel movements — but difficulty passing stool, the sense of incomplete evacuation, or consistently hard stools can qualify even when frequency seems adequate. All of these have real physiological causes that can be identified and addressed.

Types of Constipation: Why This Matters

Constipation is not one condition — it is a symptom with different underlying mechanisms. Identifying the type helps direct the right treatment.

Normal transit constipation (functional constipation): The most common type. Stool moves through the colon at a normal rate, but feels difficult to pass. Often driven by diet, hydration, stress, and lifestyle factors. Most responsive to first-line lifestyle interventions.

Slow transit constipation: The colon’s muscular contractions are reduced, slowing movement of stool. More common in women, and can be influenced by hormonal factors. May not respond as well to fiber alone and sometimes requires medication.

Outlet dysfunction constipation: A problem with the mechanics of defecation itself — the pelvic floor muscles don’t relax properly when trying to pass stool. Often associated with straining, a sensation of blockage, or the need to manually assist evacuation. Biofeedback therapy — not laxatives — is the evidence-based treatment for this type.

IBS with constipation (IBS-C): Constipation accompanied by abdominal pain and bloating that improves with bowel movements. Overlapping symptoms with functional constipation but a distinct clinical entity with its own treatment considerations.

If you have been treating constipation with lifestyle changes and laxatives for months without adequate relief, it is worth asking your physician which type you have — because treatment differs meaningfully.

What Causes Constipation?

Causes fall into two broad categories: primary (lifestyle and functional) and secondary (medical conditions and medications).

Primary / Lifestyle Causes

Insufficient dietary fiber: The average American consumes 10–15 grams of fiber per day — far below the recommended 25 grams for women and 38 grams for men. Fiber is what gives stool its bulk and water content. Without it, stool becomes compact, dry, and slow-moving. See our post on adding sugar and reducing processed food for more on how diet affects gut function.

Inadequate hydration: When the body is dehydrated, the colon draws more water from stool — making it harder and more difficult to pass. The colon is literally trying to conserve fluid at the expense of your bowel comfort.

Physical inactivity: Sedentary behavior slows colonic motility. Movement provides mechanical stimulation to the bowel and improves smooth muscle contraction. Even brisk walking has been shown to improve bowel function.

Ignoring the urge: Repeatedly suppressing the urge to defecate — a common habit in busy schedules — desensitizes the rectum over time and disrupts normal bowel signaling. When your body sends the signal, respond to it.

Sudden dietary changes: Traveling, changing eating habits, or starting a new diet can all disrupt the gut’s microbiome and motility patterns, causing temporary constipation.

Stress and the gut-brain axis: The gut has its own nervous system — the enteric nervous system — that is deeply connected to the brain via the vagus nerve. Chronic psychological stress, anxiety, and depression directly affect gut motility. Many patients notice a clear connection between high-stress periods and constipation. This is not imaginary — it is neuroscience. Our post on managing chronic stress and its health effects discusses this connection further.

Secondary Causes: Medical Conditions

A number of underlying health conditions cause or contribute to constipation and should be considered when symptoms are persistent, new, or accompanied by other concerning signs:

Hypothyroidism — one of the most common and frequently missed causes; thyroid hormone regulates GI motility
Diabetes — autonomic neuropathy from poorly controlled diabetes can impair colonic nerve function
Irritable bowel syndrome (IBS-C)
Pelvic floor dysfunction — particularly common in women who have given birth
Colorectal structural issues — polyps, strictures, or in rare cases, cancer
Pregnancy — progesterone relaxes smooth muscle throughout the body, including the colon, slowing motility
Neurological conditions — Parkinson’s disease, multiple sclerosis, spinal cord issues
Celiac disease and inflammatory bowel disease

When to see your doctor promptly: Constipation that is new, significantly changed from your baseline, accompanied by blood in the stool, unexplained weight loss, fever, severe abdominal pain, or alternates with unexplained diarrhea warrants medical evaluation — not a laxative. These symptoms may indicate a condition that needs proper diagnosis.

Secondary Causes: Medications

A 2024 analysis of the FDA Adverse Event Reporting System confirmed that drug-induced constipation accounts for approximately 11% of all treated constipation cases. The most common culprits include:

Opioid pain medications — the most significant cause of drug-induced constipation; almost universally constipating
Iron supplements — a common and clinically important cause, especially relevant for women taking iron for deficiency
Antidepressants — particularly tricyclics (amitriptyline, nortriptyline) and some SSRIs
Antipsychotics and mood stabilizers
Calcium channel blockers (used for blood pressure) — verapamil in particular
Diuretics — can cause dehydration, indirectly worsening constipation
Calcium supplements — especially at higher doses
Antacids containing aluminum or calcium (Tums, Maalox)
Antihistamines (diphenhydramine — Benadryl)
Some diabetes medications

If you started a new medication and noticed a change in your bowel habits shortly after, there is likely a connection. Discuss it with your prescribing physician — there may be alternatives, or a targeted bowel regimen can be added.

What Constipation Feels Like: Symptoms

Beyond infrequent bowel movements, chronic constipation typically includes:

Hard, lumpy, or pebble-like stools
Straining or pain during bowel movements
Sensation that you haven’t fully emptied after going
Abdominal bloating, cramping, or pressure
Lower back discomfort
Nausea or loss of appetite
Feeling sluggish or fatigued

These symptoms can significantly affect daily function, mood, and — over time — physical health through the complications discussed below.

What Actually Helps: Evidence-Based Strategies

1. Hydration — The Foundation

The colon’s primary job is water absorption. When you are under-hydrated, it pulls more water from stool — making it hard and dry. Drinking adequate fluid is the most fundamental intervention for most forms of constipation.

The National Academies of Sciences recommend approximately 91 ounces (about 11 cups) of total fluid per day for women and 125 ounces for men — from all food and beverage sources combined. If you are constipated, prioritize water over other beverages, and drink a large glass of water first thing in the morning, which can stimulate colonic activity.

Signs of adequate hydration: pale yellow urine, frequent urination. Dark urine means drink more.

2. Dietary Fiber — Both Types Matter

Increasing fiber intake is the first-line dietary recommendation for functional constipation. The goal for women is 25 grams of fiber per day — most Americans fall significantly short of this. Fiber works by adding bulk and water-holding capacity to stool, making it softer, larger, and easier to move.

Soluble fiber dissolves in water to form a gel, slowing digestion and softening stool. Sources include oats, apples, pears, beans, lentils, flaxseed, and psyllium.

Insoluble fiber does not dissolve in water — it adds bulk and helps food move through the gut faster. Sources include whole wheat, bran, vegetables, and legumes.

Practical approach: Add fiber gradually — increasing too quickly causes gas and bloating. Add one serving per day and increase over 1–2 weeks. Always pair increased fiber with increased water — fiber without adequate hydration can worsen constipation. See our post on how dietary fiber affects your metabolic health for more context.

3. Physical Movement

Regular physical activity directly stimulates colonic motility — the muscular contractions that move stool through the bowel. Even 30 minutes of moderate aerobic activity — brisk walking, cycling, swimming — can meaningfully improve constipation symptoms, particularly in sedentary individuals. If your lifestyle is primarily sedentary, adding a daily walk is one of the most clinically practical interventions available.

4. Establish a Bowel Routine

The gastrocolic reflex — the natural wave of colonic contractions that follows eating — is strongest in the morning and after meals. Taking 10–15 minutes to sit on the toilet after breakfast, whether or not you feel an urge, helps train your bowel to be responsive during its natural peak activity windows. Consistency matters more than urgency.

Also: do not ignore the urge. When your body signals it is ready, respond promptly. Chronically suppressing this reflex desensitizes the rectal stretch receptors over time, making constipation harder to resolve.

Positioning matters: A squatty posty or footstool elevating your feet 6–9 inches while on the toilet places the body in a more natural squatting position, reducing the anorectal angle and making evacuation significantly easier. This is evidence-supported and underused.

5. Probiotics and Gut Microbiome Support

The gut microbiome plays a meaningful role in bowel regularity. Emerging research confirms that altered microbial composition is associated with slow transit constipation. Probiotic-rich foods — yogurt, kefir, kimchi, sauerkraut, and kombucha — introduce beneficial bacteria that support gut motility and stool consistency.

A 2024 systematic review found that specific probiotic strains — particularly Lactobacillus and Bifidobacterium species — increased stool frequency and improved consistency in individuals with functional constipation. Dietary diversity, prebiotic foods (garlic, onions, leeks, asparagus, bananas, oats), and fermented foods together support the microbial environment that keeps bowels functioning well.

6. Prunes — More Effective Than You Think

Prunes (dried plums) are one of the most evidence-supported natural remedies for constipation. They contain both sorbitol — a natural sugar alcohol with mild osmotic laxative properties — and a unique polyphenol profile that stimulates colonic contractions. Research has shown prunes to be more effective than psyllium fiber for improving stool frequency and consistency. A serving of 4–6 prunes once or twice daily is clinically reasonable for most people.

Note for IBS sufferers: Prunes are high FODMAP and may worsen bloating and gas in people with IBS — use with caution.

7. Caffeinated Coffee

Caffeinated coffee stimulates colonic motility — research confirms it triggers contractions in the colon, typically within 20–30 minutes of consumption. This is why many people find their morning coffee reliably prompts a bowel movement. While this effect is real and useful, it should not replace hydration with water, and caffeine in excess can cause dehydration that counteracts this benefit.

8. Magnesium

Magnesium — particularly magnesium citrate and magnesium oxide — works as an osmotic agent, drawing water into the colon to soften stool and stimulate bowel movement. Magnesium citrate is the better-absorbed form and is available over the counter. For mild to moderate constipation, 200–400 mg of magnesium glycinate or citrate at bedtime is a clinically reasonable approach.

Important: Do not use magnesium laxatives if you have kidney disease — the kidneys regulate magnesium excretion, and impaired kidneys cannot safely eliminate excess amounts.

When Lifestyle Changes Aren’t Enough: Laxatives

If dietary and lifestyle interventions haven’t provided adequate relief after 2–4 weeks, laxatives are a reasonable next step. Not all laxatives are equal — and some are significantly safer for ongoing use than others.

Laxative Type	Examples	How It Works	Evidence Grade	Notes
Bulk-forming	Metamucil (psyllium), Citrucel, Benefiber	Adds bulk and water to stool	Moderate	Safest long-term; must take with plenty of water
Osmotic	MiraLAX (PEG 3350), Milk of Magnesia	Draws water into colon	Strong (Grade A)	First-line for chronic constipation; well-tolerated
Stimulant	Senna (Senokot), Bisacodyl (Dulcolax)	Stimulates bowel muscle contractions	Strong (Grade A)	Effective; use short-term; avoid daily use
Stool softeners	Docusate (Colace)	Adds moisture to stool	Weak	Less effective than commonly believed; limited RCT evidence
Lubricant	Mineral oil	Coats stool for easier passage	Limited	Not for long-term use; risk of aspiration

Per a 2024 systematic review of OTC laxative evidence, polyethylene glycol (MiraLAX) and senna have the strongest Grade A evidence supporting their use as first-line laxatives for chronic constipation. Despite being widely recommended, fiber laxatives alone showed inconsistent benefit over placebo in controlled trials — they work best when dietary fiber intake is genuinely low and hydration is adequate.

On docusate (Colace): Despite being one of the most commonly recommended stool softeners, it has the weakest evidence base of all laxative types. Multiple reviews have found it no more effective than placebo for chronic constipation. It may have limited utility as an adjunct, but it should not be a primary strategy.

On stimulant laxative dependence: The concern that senna and bisacodyl cause permanent bowel damage or dependency is largely unsupported by current evidence. However, daily long-term use is still not recommended — these are best used situationally or for short treatment courses, not as a permanent daily intervention.

Mayo Clinic’s 2024 guidance on laxatives is a helpful resource if you want to understand the options in more detail before purchasing.

The Low FODMAP Diet and IBS-Related Constipation

If your constipation is associated with significant bloating, abdominal pain, and variable bowel habits — suggestive of IBS-C — a low FODMAP diet may provide meaningful relief. FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols — a group of short-chain carbohydrates that are poorly absorbed in the small intestine and fermented by gut bacteria, producing gas and osmotic fluid shifts.

A low FODMAP approach eliminates high-FODMAP foods (wheat, garlic, onions, lactose, certain fruits) for 4–6 weeks, then systematically reintroduces them to identify individual triggers. It is one of the most evidence-supported dietary interventions for IBS and is best implemented with the guidance of a registered dietitian, as it is nutritionally restrictive and not intended for long-term exclusive use.

Note: This diet is for IBS-related symptoms, not for all types of constipation. It also eliminates many prebiotic and fiber-rich foods — so it should not be approached as a general gut health strategy.

Complications of Untreated Chronic Constipation

Long-standing constipation is not merely uncomfortable — it carries real physical risks that compound over time:

Hemorrhoids: Repeated straining increases pressure in the rectal veins, causing them to swell and bulge. Hemorrhoids can cause pain, itching, bleeding, and significant quality of life impact. They are among the most common complications of chronic constipation.

Anal fissures: Hard, dry stools passing through the anal canal can tear the delicate lining, causing sharp pain and bleeding with bowel movements. Fissures are notoriously slow to heal due to poor blood supply in the area.

Fecal impaction: Severe constipation can cause stool to become so compacted in the rectum that it cannot pass normally. This is a medical emergency requiring manual disimpaction or prescription intervention. It is more common in the elderly, in patients on opioids, and those with neurological conditions.

Diverticulitis: Chronic straining increases intraluminal pressure in the colon, which over time contributes to the formation of small pouches (diverticula) in the colon wall. If stool becomes trapped in these pouches, it can become infected — causing diverticulitis, a painful and sometimes serious condition.

Rectal prolapse: In severe cases, chronic straining can weaken the pelvic floor supports and cause rectal prolapse — the rectum protruding through the anus. This requires surgical repair.

A Note on Constipation During Pregnancy and Postpartum

Constipation is extremely common during pregnancy, affecting up to 40% of pregnant women. The causes are layered: progesterone relaxes smooth muscle throughout the body (including the colon), iron supplementation is frequently constipating, the growing uterus physically compresses the bowel, and physical activity often decreases.

Safe first-line strategies during pregnancy include increased water intake, dietary fiber, regular walking, and prunes. Docusate sodium is considered safe during pregnancy. MiraLAX (PEG 3350) is generally considered low-risk and is widely used during pregnancy, though it is technically not FDA-approved for this indication — discuss with your OB. Stimulant laxatives (senna, bisacodyl) should be used sparingly and with provider guidance during pregnancy.

See our post on healthy pregnancy and what actually matters for more on managing common pregnancy symptoms.

Postpartum constipation is also very common — particularly after cesarean section or perineal repair — and should be proactively addressed rather than endured. A combination of docusate and MiraLAX is a standard approach in the immediate postpartum period.

The Bottom Line

Constipation is common, but it is not something you simply have to live with. It has identifiable causes — dietary, lifestyle, medical, and medication-related — and evidence-based solutions at every level of severity.

Start with the fundamentals: water, fiber, movement, and a consistent bowel routine. Add probiotics, prunes, and magnesium if needed. If those measures are insufficient after several weeks, osmotic laxatives (MiraLAX) or senna are the best-supported first-line pharmaceutical options. And if constipation is chronic, significantly changed, or accompanied by concerning symptoms — blood in the stool, weight loss, severe pain, or alternating with diarrhea — see your physician. It may be a signal worth investigating.

Your gut health is part of your overall health. Treat it accordingly.

For more on gut health and how nutrition affects your body, read our posts on how dietary fiber and whole foods support your health, the gut microbiome and its role in metabolic health, intermittent fasting and digestive health, and healthy pregnancy management.

References:

Symptoms Explained

Why Am I Constipated? Learn Causes, Symptoms & What Actually Happens

What Is Constipation — Clinically Defined

Types of Constipation: Why This Matters