Medically Reviewed

Can a Multivitamin Cause Constipation? It Depends

Learn how to avoid constipation when taking a multivitamin, including which nutrients to watch out for that may cause constipation and how to avoid this issue.

So, can multivitamins really cause constipation? It depends

Used by about one third of the US population on a daily basis, multivitamins are one of the most popular supplements on the market. These supplements can support general health by ensuring you are meeting the recommended amounts of vitamins and minerals you need – and that you might not be getting from food alone.

As such a common and foundational health supplement, you might not associate multivitamins with constipation. But some are now asking: Can a multivitamin cause constipation? We want to answer this for you!

First of all, let’s define constipation. According to the National Institutes of Health, constipation may involve fewer than three bowel movements per week, stools that are dry, lumpy, or hard in form or difficult or painful to pass, and/or feeling like you haven’t fully passed the stool. Be sure to always discuss bowel changes such as constipation with your doctor as it can be a sign of other underlying health conditions.

So why might multivitamins be associated with constipation? Some of the main reasons may include the fact the multivitamin contains one or more of the following:

  • Iron or calcium, both of which may cause temporary constipation in certain forms or amounts
  • High levels of vitamin D, which can cause excess calcium absorption
  • Other ingredients that may alter gut motility

We’ll discuss each one of the reasons in more detail in this article.

It’s also important to note that not all multivitamins are created equal. So, just because one multivitamin may cause constipation, another one with a different formulation may be tolerated well. The trick is to read ingredient labels to check for certain ingredients, as well as the form of nutrients and the amounts included. Also, be sure to check ingredients to make sure you are avoiding any potential allergens, which could cause negative reactions including potentially aggravating your gut as well.

Which supplements may cause constipation

Keep an eye out for the following ingredients in multivitamins and other supplements to make an informed decision on whether or not the supplement may be right for you. You should also keep in mind that every person is unique as is their response to starting new supplements. So depending on the dose being used, the supplements can affect people differently.


Iron is an essential mineral involved in a host of functions in the body, including energy production, oxygen circulation, immune system, brain activity, and muscle function. Maintaining adequate levels of iron in the body is crucial to ensure optimal health and prevent iron-deficiency anemia.

However, you should be savvy when it comes to taking a supplement containing iron. Not all multivitamins contain iron, but some do and will often state that on the front of the label. But be sure to check the ingredients list anyway.

Supplemental iron comes in many forms. The most common form of iron is ferrous sulfate. Other forms include ferrous gluconate, ferrous fumarate, and ferrous bisglycinate. Some studies suggest that iron taken in oral supplement form can increase the production of methane gas in the gut, which is associated with the potential for constipation.

But there’s hope: iron in the bisglycinate form has been shown to be better absorbed and can increase iron levels at smaller doses than the common ferrous sulfate form.

If you experience constipation when taking a supplement or multivitamin containing iron, consider switching to one that contains the more bioavailable form of iron, ferrous bisglycinate.

Care/of’s iron supplement and multivitamin with iron both contain iron as ferrous bisglycinate, which is a chelated form of iron. Chelation prevents the mineral from interacting with other compounds, making it easier for the body to digest and absorb than non-chelated minerals.

Vitamin D

Vitamin D has become widely popular in the last decade or so as a nutrient essential for many aspects of good health. This essential vitamin plays a critical role in immune function, bone health, muscle contraction, brain function, and more.

Vitamin D helps the body absorb calcium, which is essential for building and maintaining strong bones. Without enough vitamin D, the body cannot absorb calcium well. Lack of calcium can lead to bone issues.

Adequate vitamin D also supports healthy bowel function. More research is still needed on understanding whether vitamin D deficiency can lead to constipation or whether the two issues are correlated for different reasons.

As such a pivotal nutrient, it can be tempting to think more vitamin D is better. But that’s often not the case with vitamins and minerals. Excess vitamin D can lead to excess calcium absorption. High levels of calcium in the blood may eventually reduce bowel motility and cause temporary constipation.

Vitamin D can be a helpful supplement, but only when taken within certain doses for certain periods of time. The Recommended Dietary Allowance (RDA) for vitamin D is about 15 mcg, or 600 IU, for most adults. Higher doses may sometimes be useful – but you should leave it to a medical professional to let you know when a higher dose is advisable.

Be sure to talk to your doctor about getting your vitamin D levels checked to see if you might benefit from vitamin D supplementation and how much to take. Also discuss if you have any bowel changes and concerns before taking supplements to make sure you are addressing the root cause and not just masking a symptom.


Calcium is an essential mineral and most known for its role in building strong bones. In addition, calcium is needed for muscle function and nerve transmission.

As described above, calcium absorption is dependent on vitamin D status in the body. Maintaining adequate levels of essential nutrients in the body are important to maintaining healthy bowel movements.

Too much calcium in the body can slow down gut motility through alterations in parathyroid hormone activity. Excess calcium can also compete with magnesium for absorption and transport in the body. Magnesium is a mineral essential for gut motility.

Calcium naturally occurring in foods is regarded as often better absorbed than supplemental calcium. Calcium carbonate appears to be the form of calcium associated with higher likelihood of causing changes in bowel movements like temporary constipation.

Best food sources of calcium include dairy and bone-in fish like sardines and some canned salmon. Some plant foods, such as kale and broccoli, also provide some calcium.

However, some people cannot get enough calcium from their diet, especially those who can’t tolerate dairy or are vegan. The ability to absorb calcium also decreases with age. The RDA for calcium is 1000-1200 mg. If you are not meeting these recommended intakes, it’s important to get your levels up.

If desiring to start a calcium supplement, consider a supplement using whole food sources of calcium. The calcium citrate form in some supplements is also highly absorbable and can be taken without food, but it tends to be more expensive and contain less calcium by volume. Calcium carbonate supplements are usually the least expensive, but they are also the form most associated with constipation.

There are some precautions to keep in mind when considering calcium supplementation. If you have pre-existing kidney issues, be careful with calcium supplementation and seek the guidance of your doctor. You should also take calcium supplements separately from iron supplements since they compete for absorption in the gut.


Berberine is an herbal compound not usually found in multivitamin formulations. It is often added to other supplement formulations to provide benefits like metabolic health support. According to a study done in animals, berberine can relax the involuntary muscles of the intestines and prolong the transit time of food in the gut, enabling more complete digestion and absorption.

So, if constipation or slow gut motility is already a struggle, berberine may not be a good choice. It can contribute to constipation by prolonging the intestinal transit time. However, berberine is sometimes used to correct gut bacterial imbalances that can contribute to constipation, so the appropriateness of berberine depends on your particular health needs. No studies yet exist to specifically address whether or not berberine and constipation are linked, so more research is needed in this area.

Fiber supplements

Fiber can help with occasional constipation in many people. It can promote stool frequency, and particularly insoluble fiber can increase stool bulk and shorten intestinal transit time. Fiber can help retain enough water in the intestines to make stools easier to pass.

Adequate hydration is essential when eating foods with fiber to support healthy and regular bowel movements. If you start a fiber supplement without increasing your hydration accordingly, this drastic increase in fiber can result in constipation.

To avoid this problem when taking fiber supplements, slowly work your way up to larger doses and be sure to hydrate frequently.

Folic acid

According to some sources, folic acid, or also known as folate in the biological form, folic acid deficiency is associated with occasional constipation. However, if constipation is a problem, folic acid is not the first nutrient to look to. Constipation is more commonly an issue with insufficient intake of fiber and intake of supplements containing high levels of iron and calcium.

Adequate folic acid levels can support digestive health. Folic acid deficiency can occur in those with absorption issues. With that said, always talk to your doctor about bowel changes, as they may be a sign of other serious conditions.

Which supplements may ease constipation?

Many supplements can help get your bowels moving. Which one works best will depend on what is creating constipation in your body in particular. Some specific supplements that may ease constipation include fiber powders like psyllium husk, probiotics, magnesium, aloe vera juice, and senna. Be sure to talk to your doctor or a registered dietitian to determine which supplements might be the best fit for your gut health needs.

How to avoid constipation with your multivitamin?

When deciding on the right multivitamin for you, consider which ingredients are in the supplement, including iron and calcium, and what amounts and forms these are in.

Care/of’s Multivitamin is made with high quality, non-GMO ingredients and activated forms of certain B vitamins. The Vitamin Packs also allow you to customize an easy-to-take daily pack of vitamins, minerals, and additional boosters to fit your unique nutrition needs.

And think outside of just the multivitamin itself. Are you making sure you’re eating a balanced diet with proper hydration, exercising, getting adequate sleep, and doing stress management? All of these can play a role in healthy gut motility.

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