2 Supplements That Can Cause Constipation (and What to Do About It)

Calcium and iron supplements might be the reason you're backed up.
Image Credit: Letizia Le Fur/ONOKY/GettyImages

Without question, what you eat (or don't eat) affects how frequently and how easily you poop, says Caroline Jouhourian, MD, a gastroenterologist at Lowell General Hospital in Massachusetts.


Dr. Jouhourian tells her patients that they should have "one good bowel movement every day," explaining that this will leave them feeling emptied out. Still, she says, every person is different (and it's OK if you don't go every single day!).

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When you're constipated, however, you might have three or fewer poops per week, according to the U.S National Library of Medicine.


If you're struggling to go, it may be because of something you've eaten or a supplement you've taken. Vitamin and mineral supplements have increased in popularity, with roughly half of adults in the United States taking at least one, according to a March 2013 paper in ‌JAMA Internal Medicine‌.

So if you have a few vitamin bottles sitting in your cabinet right now and you're having a hard time going number two, note that these supplements that cause constipation might be to blame.


1. Iron

Iron is an essential nutrient that helps transport oxygen from the lungs to the rest of your body, according to the National Institutes of Health (NIH).

You can get enough iron from your diet from foods like meat, leafy greens, legumes, nuts and seeds and fortified breads and cereals, but in some cases, especially for people who have periods or are breastfeeding, it's possible to become deficient, according to the National Heart, Lung and Blood Institute.


Deficiency can lead to anemia, which can cause extreme fatigue, brittle nails, cold sensitivity and shortness of breath, according to the NIH. In cases of deficiency — which is determined by a blood test — your doctor might recommend an iron supplement, which is known for causing constipation, Dr. Jouhourian says.

Constipation due to iron supplements is dose-dependent. That means the higher the dose, the more you'll experience constipation, Dr. Jouhourian says. High doses of iron — 45 milligrams per day or more — can lead to GI distress, according to the NIH. Many supplements have about 65 milligrams of iron.



Dr. Jouhourian recommends trying liquid iron, which is more easily absorbed than pills. Taking iron with vitamin C can also increase absorption.

You can also break your pill in half, and take one in the morning and one in the evening. In some cases, you can talk to your doctor about injectable iron or infusions, although those are not usually covered by insurance, Dr. Jouhourian says.


"Injectables and infusions are often used for people with known iron deficiency, not just for people who are taking iron." Dr. Jouhourian also emphasizes the importance of working with a medical professional before starting a supplement.


There are ways to reduce the risk of constipation and still get the iron you need. These iron supplements might be easier on your GI tract:

  • Heme iron polypeptides
  • Carbonyl iron
  • Iron amino-acid chelates
  • Polysaccharide-iron complexes

2. Calcium

Calcium is the most abundant mineral in the body, and when paired with vitamin D, calcium is crucial for bone development and strength, per the NIH.


It's recommended that adults get between 1,000 and 1,200 milligrams of calcium every day — and it's especially important for women to get enough calcium to fight off osteoporosis, Dr. Jouhourian says.

Like with all nutrients, it's best to eat calcium-rich whole foods before trying a supplement, Dr. Jouhourian says. A glass of milk, for example, provides calcium, protein, fat and potassium.


But there are cases when a doctor may recommend a calcium supplement, and that, in turn, could lead to constipation.

While the GI tract is not fully understood, it's thought that calcium doesn't allow for good hydration in the intestine, which then leads to constipation, Dr. Jouhourian says. That means hydration is extra important when taking a calcium supplement. Dr. Jouhourian recommends people drink 64 ounces of water per day or more if they're physically active.


Some calcium supplements may cause more GI distress than others. For example, calcium carbonate might be less tolerated than calcium citrate, according to the NIH.


If you're experiencing constipation while taking a calcium supplement, experts recommend trying calcium citrate, which is better absorbed but also has less calcium than carbonate, according to Brigham and Women's Hospital.

Tips to Avoid Constipation

Taking an iron or calcium supplement doesn't automatically relegate you to a lifetime of constipation.

In addition to finding a supplement that's easier on your GI tract — liquid iron or calcium citrate, for example — there are simple lifestyle and dietary changes you can make to avoid or lessen constipation.


If your constipation is persistent or unexplained, please seek help from your medical provider, per the Mayo Clinic.

1. Stay Hydrated

Drinking enough water will keep things running smoothly. Dr. Jouhourian points out that caffeinated tea and coffee are not the same as water, so aim for 64 ounces (eight glasses) a day or more if you're physically active.

2. Eat High-Fiber Foods

The recommended daily intake of fiber is 14 grams for every 1,000 calories, according to the Academy for Nutrition and Dietetics. So if you eat 2,000 calories a day, aim for 28 grams of fiber.

Fill your plate with high-fiber foods, including whole grains, fruits, vegetables and beans.

"Fiber is tricky," Dr. Jouhourian says. "It keeps you regular, but too little or too much can cause constipation [until your body gets used to it]."

3. Stay Active

Regular exercise — the Physical Activity Guidelines for Americans recommend 150 minutes of moderate activity per week — can increase muscle strength, which can, well, make pooping easier, according to Harvard Health Publishing.

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