Treating IBS Constipation With Magnesium

Can a mineral supplement ease your constipation?

magnesium tablets
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If you experience constipation-predominant irritable bowel syndrome (IBS-C), you may have come across the recommendation to take a magnesium supplement or a magnesium-based laxative. Before taking magnesium, or any vitamin, it is extremely important to be aware of the possible risks and benefits and to talk to your doctor about whether it would be beneficial for your specific situation.

Current Evidence

While taking magnesium is a common way of regulating bowel movements and easing constipation, there is limited evidence supporting its use as a laxative, specifically in IBS, which is classified as a functional digestive disorder.

Studies have shown that consumption of mineral water rich in magnesium sulfate can improve the frequency of bowel movements in people who have IBS-C, but the effect has not been shown to last for longer than 6 weeks.

How Magnesium May Work in Constipation

Magnesium is a mineral that is essential for overall physical health. Approximately half of the magnesium in our bodies is found in our bones. The rest serves to help in cellular functioning throughout the body’s various systems.

The laxative effect of magnesium appears to come through two different mechanisms.

Muscle Relaxation: Magnesium relaxes the muscles in the intestines, which can help to establish a smoother flow as the stool passes through the bowels.

Stool Softener: Magnesium draws water into the intestines, working as an osmotic laxative. This increase in water stimulates bowel motility. It also softens and increases the size of the stool, triggering a bowel movement and helping to make stools easier to pass.

Recommended Daily Dose

Magnesium plays an important role in muscle function, heart rhythm, blood pressure, immune system functioning, and blood sugar level. In general, most people have enough magnesium in their system and do not need to take a magnesium supplement.

The National Institutes of Health (NIH) has published a fact sheet outlining of the recommended daily intake of magnesium. The amount recommended varies by age, and different guidelines are offered for women who are pregnant or breastfeeding. Note that this is the total amount, which includes magnesium intake from foods, too.


You can take magnesium as a vitamin pill, in a prepared liquid form, or as a powder that you mix to make a liquid.

Magnesium supplements come in a variety of forms, with the most popular being citrate, chelate, and sulfate. There does not appear to be any significant health or absorption differences among the various kinds.

If you have IBS-C, avoid magnesium supplements that contain calcium as the added calcium may increase constipation. If you need calcium for other health reasons, work with your doctor to find a calcium dosage that won't compound your condition.

Side Effects and Interactions

While people often assume you cannot overdose on vitamin or mineral supplements, taking excessive amounts can, in fact, have serious consequences.

Magnesium can produce side effects, medication interactions, and toxicity. If you use it, be sure to discuss your recommended dose with your doctor, even when you use an over-the-counter formulation.

IBS Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

Doctor Discussion Guide Man

Side Effects: The most common side effect is diarrhea, which can cause dehydration, nutritional deficits, weight loss, and electrolyte imbalance, potentially resulting in serious effects on your heart, muscles, and breathing.

Toxicity: Toxic amounts of magnesium can cause problems with the kidneys and may produce severe adverse events affecting the intestines. A condition called ischemic colitis, which can cause permanent damage to the intestines has been described as a result of magnesium toxicity.

Medication Interactions: Supplemental magnesium may interfere with the effectiveness of some prescription medications. Before starting magnesium, tell your doctor and pharmacist if you are taking any of the following:

  • Laxatives
  • Vitamin supplements
  • Diuretics
  • Chemotherapy drugs
  • Osteoporosis medications
  • Thyroid medications
  • Certain antibiotics, such as ciprofloxacin and moxifloxacin

In some cases, you can minimize a drug interaction by separating magnesium from the co-prescribed drug by four to six hours. In others, your doctor may need to either substitute or adjust the dose of the co-prescribed drug.

Considerations: Your kidneys are directly responsible for clearing magnesium from the blood, so you should not take vitamin and mineral supplements (unless prescribed by your doctor) if you have kidney disease or if you need dialysis, as even normal amounts may produce toxicity.

If your kidneys are impaired, the excessive intake of magnesium can lead to an abnormal accumulation referred to as hypermagnesemia. This, in turn, can lead to heart rhythm problems, respiratory distress, and even cardiac arrest.

A Word From Verywell

If you are using magnesium to treat your constipation from IBS-C, you should be aware that magnesium used to treat constipation is not intended to be used as a dietary supplement.

You should also be careful about taking a magnesium supplement if you are regularly taking antacids or laxatives containing magnesium. Read the product labels carefully to prevent excessive magnesium intake.

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