∿ Digestive Health Resource
Why Am I Constipated? A Pharmacist’s Guide to Causes, Relief, and When to Get Help
By Eddie Khoriaty, BPharm, R.Ph., C.Ph.
Constipation is one of those health problems almost everyone experiences at some point, yet many people have no idea what actually counts as constipation, what causes it, or what they should do about it. You might go several days without a bowel movement, or your stool may suddenly become hard and difficult to pass. You might feel bloated, uncomfortable, or as though you haven’t completely emptied your bowels even after going to the bathroom.
One of the first things I think about in this situation is something people frequently overlook: What changed?
Did you start a new medication or supplement? Change your diet? Begin eating more protein and less fiber? Start taking iron or calcium? Travel? Become less active? Drink less water? Have an illness?
Constipation isn’t always about needing more fiber. In fact, understanding why you’re constipated is often more useful than immediately reaching for a laxative.
This guide explains the most common causes of constipation in adults, the medications and supplements that can contribute to it, how different over-the-counter laxatives work, where fiber, magnesium and probiotics may fit, and when constipation deserves medical attention.
At a Glance
Key Takeaways
- Constipation is not defined only by how often you go. Hard stools, straining, difficulty passing stool, and feeling incompletely emptied also matter.
- When constipation begins suddenly, start by asking what recently changed, including medications, supplements, diet, hydration, activity, travel, or routine.
- Not all laxatives work the same way. Fiber supplements, osmotic laxatives, stimulant laxatives, and stool softeners have different uses and levels of supporting evidence.
- Constipation accompanied by bleeding, severe or persistent pain, vomiting, fever, inability to pass gas, or unexplained weight loss requires medical attention.
What Does Constipation Actually Mean?
Many people assume they are constipated if they don’t have a bowel movement every day, but that isn’t necessarily true. Normal bowel habits vary considerably from one person to another. Some healthy people have multiple bowel movements each day, while others may go only several times per week.
Constipation generally involves one or more of the following:
- Fewer than about three bowel movements per week
- Hard, dry, or lumpy stools
- Straining or difficulty passing stool
- Pain during a bowel movement
- Feeling that you haven’t completely emptied your bowels
- Feeling as though stool is “stuck” or difficult to pass
What’s normal for you also needs to be considered. A significant change from your usual bowel pattern can be important even if you don’t technically meet a textbook definition of constipation.
It’s also helpful to know just how common constipation is. The National Institute of Diabetes and Digestive and Kidney Diseases estimates that about 16% of adults experience symptoms of constipation, with the condition becoming substantially more common among adults age 60 and older.
What Causes Constipation in Adults?
Constipation isn’t one condition with one single cause. It usually develops when stool moves too slowly through the digestive tract, allowing the colon to absorb more water. The longer the transit time, the more water is pulled out, leaving stool that is dry, hard, or difficult and painful to pass.
Several factors can contribute to constipation.
Not Enough Dietary Fiber
Fiber helps provide structure and bulk to stool and can support regular bowel movements. Diets dominated by highly processed foods, with relatively few fruits, vegetables, whole grains, legumes, nuts, and seeds, may not provide enough fiber.
Not Drinking Enough Fluid
Hydration is particularly important when increasing your fiber intake. Adding a large amount of fiber without adequate fluid may not produce the result you’re expecting and can sometimes leave you feeling even more uncomfortable.
Changes in Routine
Travel is a classic example. Changes in meal timing, sleep, activity, hydration, and bathroom habits can temporarily disrupt your normal bowel pattern.
Ignoring the Urge to Go
Repeatedly postponing bowel movements can contribute to constipation. When your body signals that it’s time to have a bowel movement, try not to routinely ignore that signal.
Lack of Physical Activity
Regular movement helps support gastrointestinal motility. Becoming significantly less active because of illness, injury, work habits, or aging can contribute to constipation.
Medical Conditions
Persistent constipation can sometimes be associated with conditions including hypothyroidism, diabetes, irritable bowel syndrome, neurological disorders, and pelvic floor dysfunction. That’s one reason chronic or unexplained constipation shouldn’t simply be treated indefinitely without considering the underlying cause.
At a Glance
Common Contributors to Constipation
Not Enough Fiber
A diet low in plant foods may not provide enough bulk to support regular stools.
Too Little Fluid
Inadequate hydration can contribute to stools becoming harder and more difficult to pass.
Routine Changes
Travel and changes in meals, sleep, or bathroom habits can disrupt your normal pattern.
Ignoring the Urge
Frequently postponing a bowel movement may make constipation more likely.
Less Physical Activity
Reduced movement due to illness, injury, work habits, or aging may slow bowel activity.
Medical Conditions
Thyroid, metabolic, neurological, or bowel-function disorders can contribute.
Why Am I Constipated All of a Sudden?
When someone who is normally regular suddenly becomes constipated, I like to begin by asking what changed recently.
Ask yourself:
- Did I start a new medication?
- Did the dose of one of my medications change?
- Did I start taking iron, calcium, or another supplement?
- Am I eating differently?
- Am I drinking less water?
- Have I been traveling?
- Am I exercising less?
- Have I been sick or under unusual stress?
Sometimes the explanation becomes fairly obvious once you look at constipation this way. However, a new and persistent change in bowel habits, particularly when accompanied by other symptoms, deserves evaluation by a healthcare professional.
The Pharmacist’s Question: Could Your Medication Be Causing Constipation?
This is one of the most commonly overlooked causes of constipation. Before adding another medication to treat the problem, I recommend reviewing everything you’re already taking.
That includes:
- Prescription medications
- Over-the-counter medications
- Vitamins
- Minerals
- Herbal products
- Dietary supplements
A medication doesn’t necessarily have to cause severe constipation on its own to matter. Several mildly constipating medications taken together can sometimes produce a significant effect.
Opioid Pain Medications
Opioids are among the medications most strongly associated with constipation. These drugs slow gastrointestinal motility, and the constipation may persist for as long as the opioid is being used. People taking opioids regularly should discuss constipation prevention and treatment with their healthcare professional rather than waiting until symptoms become severe.
Iron Supplements
Iron is another common culprit because some forms and doses can cause constipation, abdominal discomfort, nausea, and darker stools. If iron is causing significant constipation, don’t simply stop taking it if it was prescribed to treat an iron deficiency. Talk with your pharmacist or healthcare provider about the formulation, dose, and possible alternatives.
Calcium Supplements
Calcium supplements can contribute to constipation in some people. This is another reason I recommend looking at your entire supplement routine rather than evaluating each product in isolation.
Anticholinergic Medications
Medications with anticholinergic effects can slow bowel activity. This category includes medications used for a wide variety of conditions, including bladder symptoms, allergies, motion sickness, and certain neurological or psychiatric conditions.
Certain Antacids
Antacids containing calcium or aluminum may contribute to constipation. Interestingly, magnesium-containing products may have the opposite effect and loosen stools. That difference illustrates why simply saying “antacids cause constipation” isn’t specific enough. The ingredients matter.
Certain Blood Pressure Medications
Some medications used to treat high blood pressure, particularly calcium channel blockers, can contribute to constipation.
Certain Antidepressants
Some antidepressants, especially those with greater anticholinergic effects, can cause constipation.
Fiber for Constipation: More Isn’t Always Better
“Eat more fiber” is probably the most common advice given for constipation. It is often good advice, but it doesn’t always tell the entire story. Adults generally need about 22 to 34 grams of fiber per day, depending on factors such as age and sex.
Fiber-rich foods include:
- Beans and lentils
- Vegetables
- Berries
- Pears and apples
- Whole grains
- Oats
- Nuts and seeds
Fiber supplements such as psyllium can also be useful for some people, but there is an important practical point to keep in mind: Increase fiber gradually.
Going from a relatively low-fiber diet to a very high-fiber diet overnight can result in gas, abdominal pressure, and bloating. That can leave someone wondering, “I started eating more fiber for my constipation, so why does my stomach feel even worse?”
The fiber isn’t necessarily the problem. The amount and speed of the increase may be.
Why Can Fiber Make Constipation and Bloating Feel Worse?
Certain types of fiber are fermented by intestinal bacteria, which can produce gas. If you’re already constipated and stool is moving slowly through the intestine, suddenly adding a large amount of fermentable material may make you feel fuller and more bloated before bowel regularity improves.
A better strategy is often to increase fiber gradually, drink adequate fluids, and pay attention to how your body responds. It’s also important to remember that not every case of constipation is caused by inadequate fiber.
Someone with a medication-induced motility problem, pelvic-floor disorder, or another underlying condition may not solve the problem simply by eating additional bran.
Which Type of Laxative Should I Take?
This is where understanding the medication becomes important. “Laxative” doesn’t refer to just one type of drug. Different laxatives work in different ways, and choosing the right category can make a significant difference.
1. Bulk-Forming Fiber
Examples include:
- Psyllium
- Methylcellulose
- Calcium polycarbophil
These products absorb water and increase stool bulk. They may be particularly useful when dietary fiber intake is low.
Take fiber supplements with adequate fluid unless a healthcare professional has instructed you otherwise. Increasing fiber too quickly can also cause gas and bloating.
2. Osmotic Laxatives
Osmotic laxatives increase the amount of water retained in the intestinal tract, helping make stool softer and easier to pass.
One of the most commonly used examples is polyethylene glycol, or PEG 3350. PEG has strong evidence supporting its use for chronic idiopathic constipation. The joint American Gastroenterological Association and American College of Gastroenterology guideline gave PEG a strong recommendation for adults with this condition.
Other osmotic products include:
- Magnesium-based laxatives
- Lactulose
How quickly an osmotic laxative works depends on the product, but these medications can be useful when constipation requires more than dietary changes alone.
3. Stimulant Laxatives
Examples include:
- Bisacodyl
- Senna
- Sodium picosulfate
These products stimulate intestinal activity and can produce a bowel movement relatively quickly. A joint guideline from the American Gastroenterological Association (AGA) and the American College of Gastroenterology (ACG) strongly recommends bisacodyl or sodium picosulfate for short-term or rescue therapy in adults with chronic idiopathic constipation. Stimulant laxatives are not automatically “bad,” despite their sometimes-negative reputation. The more important questions are why you need one, how often you are using it, and whether persistent constipation needs further evaluation.
4. Stool Softeners
Docusate is probably the best-known stool softener. These products are intended to make stool easier to pass. However, one interesting point from a pharmacist’s perspective is that widespread use doesn’t necessarily mean strong clinical evidence.
The recent AGA/ACG chronic constipation guideline evaluated numerous therapies but did not make a recommendation for docusate because of insufficient evidence within the guideline review. That's a useful reminder that the most familiar OTC product isn't always the product with the strongest evidence.
Know the Difference
Osmotic vs. Stimulant Laxatives
Osmotic Laxatives
How They Work
Help draw or retain water in the bowel, making stool softer and easier to pass.
Common Examples
Polyethylene glycol, magnesium-based laxatives, and lactulose.
When They May Be Used
May be appropriate for recurring constipation, depending on the person and product.
Stimulant Laxatives
How They Work
Stimulate intestinal activity to help move stool through the bowel.
Common Examples
Bisacodyl, senna, and sodium picosulfate.
When They May Be Used
May be useful when faster relief or short-term rescue therapy is needed.
The goal isn’t simply to produce a bowel movement. If you repeatedly need laxatives just to go, don’t keep escalating treatment without discussing the problem with a healthcare professional. The underlying cause may need attention.
Magnesium and Probiotics
Can Magnesium Help With Constipation?
Yes, certain forms of magnesium can have a laxative effect. Magnesium compounds can increase the amount of water in the intestinal tract, which can soften stool and promote bowel movements. The AGA and ACG guideline conditionally suggests magnesium oxide as an option for chronic idiopathic constipation.
The important distinction is that a magnesium supplement and a magnesium laxative aren’t necessarily interchangeable. The form of magnesium and the amount consumed both make a difference. Some forms are much more likely to cause loose stools than others, and more magnesium isn’t automatically better.
People with kidney disease or impaired kidney function should be particularly cautious because magnesium is cleared through the kidneys, and excessive accumulation can be dangerous. If you’re considering magnesium specifically to treat constipation, especially if you take other medications or have kidney problems, ask your pharmacist or healthcare provider which product and dose may be appropriate.
Can Probiotics Help With Constipation?
Possibly, but not always. This is an area where marketing often gets ahead of the actual science.
Your intestinal microbiome influences digestion and gastrointestinal function, so researchers have naturally investigated whether altering gut bacteria with probiotics can improve constipation. Some clinical studies and systematic reviews have found improvements in bowel-movement frequency and certain constipation symptoms, but results vary substantially between studies.
That’s important because “probiotic” isn’t one ingredient. Different products may contain completely different:
- Species
- Strains
- Combinations of organisms
- Doses
A 2022 systematic review and meta-analysis of randomized trials found that certain probiotics may improve treatment response, stool frequency, and overall constipation symptoms. However, the researchers also emphasized the considerable variation among studies and the need for caution when interpreting the findings. More recent analyses have likewise reported possible improvements while noting limitations in the certainty and consistency of the evidence.
Because of this, I wouldn’t describe probiotics as a replacement for established constipation treatments. I would describe them as a potentially useful part of digestive-health support for some people, with benefits that appear to depend on the strain and product.
When selecting a probiotic, look beyond the enormous CFU number printed on the front of the bottle. The organisms, strains, formulation, storage requirements, and evidence behind the product matter more than simply choosing the largest number. Our guide to choosing a probiotic explains what to compare before you buy.
If you’re interested in a probiotic formulated for daily digestive support, you can also learn more about GILA Balance Probiotic and the four strains included in its formula.
DAILY DIGESTIVE SUPPORT
Meet GILA Balance
GILA Balance provides 40 billion CFU per serving from four probiotic strains, paired with prebiotic FOS and MAKTREK® Bi-Pass Technology to support everyday digestive and gut health.
- 40 billion CFU per serving
- Four probiotic strains with prebiotic FOS
- MAKTREK® Bi-Pass Technology for protective delivery
GILA Balance is designed for daily digestive support and is not intended to treat constipation. Individual responses to probiotic products can vary.
Constipation in Older Adults
Constipation becomes increasingly common with age, but it shouldn’t automatically be dismissed as “just getting older.” Older adults may be more susceptible because several risk factors frequently occur together:
- Lower fiber intake
- Reduced fluid intake
- Less physical activity
- Multiple medications
- Calcium or iron supplementation
- Chronic medical conditions
- Changes in intestinal motility
A careful medication review becomes particularly important. A person taking six, eight, or ten medications may not have one obvious constipation-causing drug. Instead, several medications may each contribute a little, creating a larger combined effect.
That’s where the advice of a pharmacist can be especially helpful. Rather than simply asking, “What can I take for constipation?” consider asking, “Could anything I’m already taking be contributing to my constipation?”
Constipation With Bloating
Constipation and bloating frequently occur together. When stool moves slowly through the gastrointestinal tract, gas and intestinal contents may remain present longer, contributing to abdominal fullness, pressure, and discomfort.
Some people respond by rapidly increasing their fiber intake. However, suddenly adding a large amount of fiber can temporarily increase fermentation and gas, making the bloating feel even worse.
Because of this connection, constipation and bloating often need to be considered together rather than treated as completely separate digestive problems.
If bloating is one of your main symptoms, read our pharmacist’s guide, Why Am I So Bloated? Do Probiotics Help and What Actually Works, for a closer look at trapped gas, food triggers, gut motility, and probiotics.
A Pharmacist’s Step-by-Step Approach to Occasional Constipation
For an otherwise healthy adult experiencing uncomplicated occasional constipation, I generally think about the problem in this order:
- Ask what changed.
Think about recent changes involving medications, supplements, diet, hydration, physical activity, travel, illness, or your normal routine. - Take an honest look at your diet.
Are you getting enough fiber from fruits, vegetables, legumes, whole grains, nuts, and seeds? If not, increase fiber gradually rather than dramatically changing your diet overnight. - Pay attention to hydration.
Fiber works best when you consume adequate fluids. Adding more fiber without enough fluid may not give you the result you expect. - Move your body.
Regular physical activity may help support normal gastrointestinal motility. Even modest movement can be a useful part of your daily routine. - Don’t repeatedly ignore the urge to go.
Establishing a regular bathroom routine may help. Some people find it useful to try having a bowel movement after breakfast or another meal, when the body’s natural gastrocolic response can stimulate colon activity. - If you need an OTC product, choose it based on how it works.
Don’t simply grab whichever laxative happens to be at eye level. Fiber supplements, polyethylene glycol, magnesium-containing products, and stimulant laxatives don’t all do the same thing. Your pharmacist can help you choose an appropriate option. - If the problem keeps returning, investigate why.
Repeatedly treating constipation without understanding its cause can mask an underlying medication issue, medical condition, or bowel-function disorder.
Keeping a short record can make it easier to spot patterns and explain what has been happening to your pharmacist or healthcare provider.
Free Digestive Regularity Tracker
Not sure what may be contributing to constipation? Use this two-page printable to track bowel habits, bloating, water intake, movement, fiber, and products used for seven days. Then bring it to your pharmacist or healthcare provider to help identify patterns and recent changes.
When to Seek Help
When Is Constipation Serious?
Most occasional constipation isn’t dangerous. However, certain symptoms should not be treated with repeated over-the-counter laxatives without medical evaluation.
Seek prompt medical attention if constipation occurs with:
- Blood in the stool
- Rectal bleeding
- Persistent or severe abdominal pain
- Vomiting
- Fever
- Inability to pass gas
- Unexplained weight loss
- Significant abdominal swelling
A persistent, unexplained change in bowel habits also deserves evaluation, particularly in an older adult or someone with a personal or family history that increases colorectal-cancer risk.
The Pharmacist’s Bottom Line
Constipation sounds simple until you start asking why it’s happening. Sometimes the answer is straightforward: not enough fiber, inadequate hydration, travel, or a temporary change in routine. But sometimes the answer may be sitting right in your medicine cabinet. An opioid, iron supplement, calcium product, anticholinergic medication, or another drug may be slowing your digestive system.
That’s why my advice isn’t simply, “Take a laxative.” Begin by identifying the likely cause, then choose an approach that makes sense for that cause.
For many people, gradually increasing fiber, staying adequately hydrated, maintaining regular physical activity, and establishing consistent bathroom habits can make a meaningful difference. When medication is needed, understanding the differences among fiber supplements, osmotic laxatives, stimulant laxatives, and other options can help you make a more informed decision.
If constipation is persistent, suddenly different from your normal pattern, or accompanied by warning signs, don’t keep treating it yourself indefinitely.
Constipation is a symptom. Sometimes the most important step is figuring out what your body is trying to tell you.
Frequently Asked Questions
How many days without pooping is considered constipation?
There isn’t one universal number because normal bowel frequency varies from person to person. Fewer than three bowel movements per week is commonly used as one definition, but stool consistency, difficulty passing stool, and changes from your normal pattern also matter.
Why am I suddenly constipated?
Common explanations include medication changes, new supplements, dehydration, dietary changes, travel, reduced activity, and changes in routine. Persistent or unexplained constipation should be discussed with a healthcare professional.
How much fiber should I eat for constipation?
General recommendations for adults range from about 22 to 34 grams per day, depending on age and sex. Increase fiber gradually and make sure you are also consuming adequate fluids.
Can too much fiber make constipation worse?
Suddenly increasing fiber can cause considerable gas and bloating. Adding fiber without adequate fluid may also be counterproductive and make constipation worse. More fiber doesn’t automatically mean better.
Which medications commonly cause constipation?
Common contributors include opioid pain medications, iron supplements, calcium supplements, medications with anticholinergic effects, certain antidepressants, calcium-channel blockers, and antacids containing calcium or aluminum.
Is MiraLAX an osmotic or stimulant laxative?
MiraLAX contains polyethylene glycol 3350, or PEG, and is an osmotic laxative. It works differently from stimulant laxatives such as bisacodyl and senna.
Is magnesium good for constipation?
Some magnesium products can have an osmotic laxative effect. However, the form and dose matter, and magnesium may not be appropriate for everyone, particularly people with impaired kidney function. Ask your pharmacist or healthcare provider before using magnesium specifically to treat constipation.
Can probiotics help with constipation?
Possibly. Research suggests that certain probiotic strains or products may improve bowel frequency or constipation symptoms in some people, but results are inconsistent. Probiotics shouldn’t be considered interchangeable simply because they all carry the word “probiotic” on the label.
When should I worry about constipation?
Seek prompt medical attention if constipation occurs with rectal bleeding, blood in the stool, severe or persistent abdominal pain, vomiting, fever, inability to pass gas, significant abdominal swelling, or unexplained weight loss. Persistent constipation or an unexplained change from your normal bowel habits also deserves medical evaluation.
Related Resources
Continue Exploring Digestive Health:
Constipation rarely exists in isolation. These related resources can help you better understand your digestive health:
Why Am I So Bloated? Learn more about trapped gas, food triggers, gut motility, and probiotics.
How to Choose a Probiotic Find out how to compare probiotic strains, CFU counts, formulations, and storage requirements.
What Is Elemental Magnesium? Learn why the form, elemental amount, and serving size all matter when comparing magnesium products.
Ask the Pharmacist Submit a medication or supplement question for pharmacist guidance.
References
- National Institute of Diabetes and Digestive and Kidney Diseases. Definition and Facts for Constipation.
- National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms and Causes of Constipation.
- National Institute of Diabetes and Digestive and Kidney Diseases. Treatment for Constipation.
- National Institute of Diabetes and Digestive and Kidney Diseases. Eating, Diet, and Nutrition for Constipation.
- Chang L, Chey WD, Imdad A, et al. American Gastroenterological Association and American College of Gastroenterology Clinical Practice Guideline: Pharmacological Management of Chronic Idiopathic Constipation. American Journal of Gastroenterology. 2023;118(6):936–954.
- van der Schoot A, Drysdale C, Whelan K, Dimidi E. Probiotics and synbiotics in chronic constipation in adults: A systematic review and meta-analysis of randomized clinical trials. Clinical Nutrition. 2022;41(12):2759–2777.
- Ding F, Hu M, Ding Y, et al. Efficacy in bowel movement and change of gut microbiota on adult functional constipation patients treated with probiotics-containing products: A systematic review and meta-analysis. BMJ Open. 2024;14.
Have More Questions About Constipation?
Questions about medications that may cause constipation, choosing an over-the-counter laxative, increasing fiber, or whether magnesium is appropriate for you? Ask Eddie, our pharmacist, for clear, evidence-based information to help you make a more informed decision.
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Medical Disclaimer
The information provided in this article is intended for educational purposes only and should not be considered medical advice. It is not intended to diagnose, treat, cure, or prevent any disease, or to replace the advice of your physician or other qualified healthcare provider.
Always consult your healthcare provider before making changes to your diet, exercise routine, medications, or supplement regimen, especially if you have a medical condition, are pregnant or nursing, or take prescription medications.
Individual health needs vary, and the information presented may not be appropriate for every person.