Constipation is typically related to diet and lifestyle, but it may also be caused by some supplements and medications. Whether it’s a vitamin, mineral or even herbal supplement, there are some that can do more harm than good for healthy bowel movements. Instead of leaning on unregulated (and often expensive) supplements, aim for a food-first approach that prioritizes whole, nutrient-dense foods. Nutrients like fiber in foods—alongside plenty of water—can help get things moving naturally, and help support your overall health. 

We spoke with the experts to get the scoop on which supplements you may want to avoid if you struggle with constipation. 

5 Supplements That Could Actually Make Constipation Worse

1. Calcium Supplements

“I’ve had several clients complain of constipation, and after a further evaluation, found that the source of their constipation was their calcium supplement,” says Kerry Conlon, M.S., RD, a digestive disease dietitian. 

Calcium supplements may worsen constipation because they slow down intestinal motility, which is just a scientific way of saying how food moves through your digestive tract. Calcium may also interfere with how much fluid is secreted in the gut, causing stools to become hard, dry and more difficult to pass.

If you’re supplementing with high doses of calcium and not drinking enough water or eating enough fiber, you’re more likely to experience constipation. “Of course, there are instances where supplementation may be essential, like calcium supplementation for osteoporosis, so talk to your doctor and a dietitian to see what options may be available for you,” recommends Conlon. 

2. Iron Supplements

Iron supplements commonly cause constipation, so if you’re iron-deficient, you may want to consider a food-first approach depending on the severity. 

“While it’s true that around 40% of women of reproductive age are iron-deficient, I’d use caution before diving into an iron supplement. Iron is one of the top supplements that can cause constipation,” says Dr. Ashley Dwyer, Pharm.D., founder of BDN Coaching. Instead, Dwyer recommends increasing your intake of foods rich in iron (such as legumes, leafy greens, fish and red meat) and vitamin C (like citrus, fruit, leafy greens and peppers) first. 

“Ferrous sulfate is the most common iron supplement that you’ll find in stores. Taking this type of iron supplement on an empty stomach or at a higher dose can lead to constipation,” Rhyan Geiger, RDN, a Phoenix-based dietitian, tells EatingWell. If you must take an iron supplement, try taking it with food and consider splitting it into smaller doses throughout the day. 

3. Fiber Supplements

Believe it or not, fiber supplements may worsen constipation in some people depending on the circumstances.

“Based on current research, fiber appears to benefit constipation for most generally healthy adults, and it's one of the main treatments for constipation,” says Kelsey Costa, M.S., RDN, a registered dietitian and science communications officer at Examine. 

“However, simply increasing fiber intake or using supplements may not always help with bowel movements, depending on the root cause of constipation,” Costa adds. 

“Fiber supplements can bulk up the stool too much and cause constipation, especially a supplement high in insoluble fiber,” says Geiger. Increasing fiber intake too quickly may also worsen constipation. “Fiber absorbs water in the digestive system, so if you consume a lot of fiber without increasing your water intake, stools can become harder to pass, making constipation worse,” Costa tells EatingWell. 

4. Vitamin D Supplements

When consistently taken in higher doses, vitamin D supplements may lead to digestive issues such as constipation. Too much vitamin D can increase the amount of calcium circulating in your blood, and as we mentioned above, too much calcium in the body may also worsen constipation.

If you’re taking a vitamin D supplement, talk with your doctor or dietitian to make sure your dose is right for you. Be sure to drink plenty of water and eat a variety of whole, nutrient-dense foods to support a healthy gut. 

5. Senna

Senna is an herbal supplement used for treating constipation due to its strong laxative effect. However, it may cause digestive issues and worsen constipation when used too frequently. 

“Like many other laxatives, long-term or excessive use of senna may lead to serious reactions and side effects, including dependence on laxatives, chronic constipation and loss of normal bowel function,” says Costa. “This appears to occur because the intestines become used to the laxative stimulation and lose their ability to contract normally without it,” she adds.  

Relying on senna too frequently may also cause fluid loss and electrolyte imbalance, “which can lead to dehydration and may contribute to constipation when not in use,” Costa tells EatingWell.

Other Ways to Help Relieve Constipation 

There are several things you can do to relieve constipation and support gut health instead of relying on supplements. Habits like eating more fiber, drinking more water and finding ways to be active may all help relieve constipation. 

Eat a variety of whole, nutrient-dense foods including fruits, vegetables, whole grains and fermented foods that contain probiotics such as miso, kefir, kimchi and sauerkraut. “Fruits, vegetables and whole grains contain fiber that support digestion,” says Conlon. These foods also offer a range of other essential nutrients and bioactive compounds, including essential vitamins, minerals, phytochemicals and antioxidants, that support our overall health.

Research suggests that regular movement should be part of the treatment for constipation. Try to incorporate more daily movement in whatever way possible, whether it’s walking, yoga, biking or something else that you enjoy and can see yourself sticking with. 

The Bottom Line

Constipation is often affected by diet, lifestyle and some supplements and medications. Experts recommend a food-first approach before turning to high-priced and unregulated supplements. In fact, some supplements like calcium, iron, vitamin D and senna may actually worsen constipation symptoms. While fiber is usually helpful for improving it, fiber supplements may worsen constipation if you increase your intake quickly and are not drinking enough water. To help relieve constipation, try to eat more whole foods, drink more water and stay active.