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Does Magnesium Cause Constipation?



Magnesium does NOT cause constipation.

More Info: When referring to intake, magnesium does not cause constipation.  In fact, magnesium is often used as a laxative.  When referring to deficiency, magnesium can cause constipation if the body is deficient in the mineral. [1]

Magnesium Has a Laxative Affect

Dietary magnesium is important to more than 300 biochemical reactions in the body.  Pharmacological magnesium is often recommended or prescribed to correct a deficiency, but it is also often prescribed as a laxative. [2]

An example of magnesium being used as a laxative is magnesium citrate.  Magnesium citrate is a saline laxative that works by increasing water in the intestines. It is often used medicinally to clean a patient’s bowels before surgery. Another example of magnesium being used as a laxative is magnesium hydroxide, commonly known as Milk of Magnesia, which is often used to alleviate occasional constipation. [3][4]

How Magnesium Works to Relieve Constipation

Magnesium is absorbed in the small intestine.  To grasp how magnesium stimulates the digestive track, it helps to understand how the digestive system works. The small intestine is a tube lined with mucosa.  Magnesium is absorbed through the mucosa to the epithelial cells and into the bloodstream. [5] A laxative such as magnesium citrate draws water FROM the tissues INTO the small intestines.  This extra water stimulates the forward movement of the intestines. [6]

Calcium Magnesium and Constipation

Because pharmacological magnesium (versus dietary) has a laxative effect, it is often prescribed in addition to calcium supplementation, which can cause constipation.  The same concept works in reverse.  Calcium supplementation may be prescribed with magnesium supplementation to offset the laxative effect of magnesium. [7]

Digestive Side Effects of Magnesium

If excessive amounts of pharmacological magnesium are ingested, such as that found in supplements, Epsom salts, or laxatives, side effects can occur.  The most common side effects are upset stomach, diarrhea, nausea, and vomiting.

More serious side effects include low blood pressure, irregular heartbeat, slowed breathing, confusion, coma, and even death. [8]


[1] European Journal of Clinical Nutrition; Murakami K
Association between dietary fiber, water and magnesium intake and functional constipation among…
2007; Volume:61; No:5; Pages:616-622

[2] Office of Dietary Supplements-National Institutes of Health

[3] WebMD
Magnesium Citrate

[4] Medline Plus-National Institutes of Health
Magnesium Hydroxide

[5] National Digestive Diseases Information Clearinghouse
Your Digestive System and How It Works

[6] American Cancer Society
Magnesium Citrate

[7]Acu-Cell Nutrition
Calcium and Magnesium

[8] Medline Plus-National Institutes of Health


Glossary of Terms

Epithelial cells: Epithelia are formed of cells that line the cavities in the body and also cover flat surfaces.
Biology at Davidson

Mucosa: is moist tissue that lines certain parts of the inside of your body. It is in your nose, mouth, lungs, and the urinary and digestive tracts.
Medline Plus

Pharmacological: pertaining to the science of drugs, including their composition, uses, and effects

Saline: consisting of or containing salt.

Expert Opinion

“It is extremely important that readers speak with their primary care physician before taking supplemental magnesium because it is excreted through the kidneys. If an individual suffers from a kidney disorder, he or she could be at risk for an excess of the mineral in the system.”
Magnesium May Help Constipation   Dr. Peter Gott

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