Magnesium for Constipation: Should I Try It?

Trang Tran, PharmD
·12 min read
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A pharmacist explains its effectiveness and safety

Medically reviewed by Suzanne Fisher, RD

Constipation is defined as having infrequent passage of stools or difficulty eliminating stools. About 15% of the population experience it, with a higher prevalence in people designated female at birth and 65 and above.

Common symptoms of constipation include the following:

Inadequate fluid and fiber intake and lack of physical activity are some of the causes of constipation.

Other causes include metabolic disturbances, medications, neurological disorders, muscle-related diseases, and structural disorders, as follows:

Regular bowel movements are essential for digestive health because they help remove waste products from your body and prevent the build-up of toxins.

The following article covers the uses of magnesium for constipation and its safety concerns.

<p>Fiordaliso / Getty Images</p> A female in a yellow shirt with a glass of water and taking vitamins.

Fiordaliso / Getty Images

A female in a yellow shirt with a glass of water and taking vitamins.

What Is Magnesium?

Magnesium is a nutrient and mineral that plays a vital role in many processes in the body, including the following functions:

  • Regulates muscle and nerve function

  • Regulates blood sugar levels

  • Regulates blood pressure

  • Regulates heart rhythm

  • Makes protein, DNA, and RNA (nucleic acids that carry out cellular processes such as gene regulation and expression)

  • Contributes to the structural development of bone

How Much Magnesium Do I Need?

The amount of magnesium that you need daily depends on your age and other factors, such as the following:

  • 51 years old and older: 420 milligrams (mg) for males; 320 mg for females

  • 31–50 years old: 420 mg for males; 320 mg for females or lactation; 360 mg for pregnancy

  • 19–30 years old: 400 mg for males; 310 mg for females or lactation; 350 mg for pregnancy

  • 14–18 years old: 410 mg for males; 360 mg for females or lactation; 400 mg for pregnancy

  • 9–13 years old: 240 mg for both males and females

  • 4–8 years old: 130 mg for both males and females

  • 1–3 years old: 80 mg for both males and females

What Are the Different Forms of Magnesium?

Magnesium comes in the following forms:

Magnesium in aspartate, citrate, lactate, and chloride forms is generally more easily absorbed than the oxide and sulfate forms.

What Are Food Sources of Magnesium?

Foods are a fantastic way to get your magnesium needs met. Foods that are sources of magnesium include the following:

  • Pumpkin seeds, roasted, 1 ounce (156 mg per serving)

  • Chia seeds, 1 ounce (111 mg per serving)

  • Almonds, dry roasted, 1 ounce (80 mg per serving)

  • Spinach, boiled, 4 ounces (78 mg per serving)

  • Cashews, dry roasted, 1 ounce (74 mg per serving)

Magnesium Deficiency

Certain medical conditions, such as alcoholism, poorly controlled diabetes, Crohn’s disease, ulcerative colitis, and chronic kidney disease, can increase the risk of magnesium deficiencies.

Some medications can lower magnesium levels, including the following:

Early signs of magnesium deficiency include the following:

More severe symptoms include:

The use of magnesium supplements can help address magnesium deficiencies. However, organic-bound magnesium salts such as the following are recommended for treating magnesium deficiency due to their higher absorption rate:

  • Magnesium citrate

  • Magnesium gluconate

  • Magnesium rotate

  • Magnesium aspartate

Does Magnesium Make You Poop?

Magnesium works as an osmotic laxative to relieve constipation by increasing the water content and volume of the stool. As a result of magnesium’s ability to draw water into the intestines, the stool softens, and the swollen stool stimulates intestinal motor activity, promoting bowel movements.

Several guidelines recommend the use of magnesium salts for constipation. However, some guidelines from Germany do not recommend the use of osmotic laxatives, such as magnesium hydroxide, for chronic constipation due to possible side effects.

A study was conducted in 34 female subjects with an average age of 40 and mild to moderate constipation. The results showed that using magnesium oxide for four weeks improved overall constipation symptoms. However, the sample size was small and limited to female subjects from Japan.

Another study conducted in 90 people with chronic constipation found that overall symptom improvement was observed in 69.2% of the senna group (stimulant laxative), 68.3% in the magnesium oxide group, and 11.7% in the placebo group (an inactive substance). However, the majority of the research subjects were female. Therefore, the results might not be the same in other populations.

Various magnesium salts are used as osmotic laxatives, but few studies compare the different salt forms. The following includes the recommended forms of magnesium supplements for constipation relief, their pros and cons, dosage, and more.

Magnesium Oxide

As suggested, magnesium oxide has been studied for constipation. The following includes its typical dosage and its pros and cons:

  • Dosage (adults): The general dosing is 2 grams (g) in three divided doses a day before or after meals or once before bedtime. However, a starting dose of 1 g taken as two or three divided doses a day is recommended due to the risk of high magnesium levels in the blood.

  • Pros: It is inexpensive, readily available, the doses can be easily adjusted, and it's non-habit-forming.

  • Cons: Poor absorption and prolonged use can cause high magnesium levels in the blood and worsen calcium retention in the kidneys.

Magnesium Hydroxide (Milk of Magnesia)

The following dosage of magnesium hydroxide is based on 400 mg of magnesium hydroxide per 5 milliliters (mL) suspension:

  • Adults and children 12 years of age and older: 30 mL (2 tablespoons) to 60 mL (4 tablespoons) per day

  • Children 6–11 years: 15 mL (1 tablespoon) to 30 mL per day

  • Children under 6 years of age: Requires consulting a healthcare provider

Each dose should be taken with 1 full cup of water (8 liquid ounces) once a day at bedtime or in divided doses. Pros and cons include:

  • Pros: It's available as a suspension, produces a laxative effect within half an hour to six hours, and can also be used as an antacid (but at a lower dose than the laxative dose).

  • Cons: Stomach pain, nausea, or vomiting, increased risk of high magnesium levels, low phosphate levels, and low calcium levels in the blood, and poor taste can be downsides

Magnesium Citrate

Magnesium citrate has been used for constipation as well. The following includes its typical dosage:

  • Adults and children 12 years of age and over: One-half bottle to one bottle (10 fluid ounces)

  • Children 6 to 11 years of age: One-third bottle to one-half bottle

  • Children under 6 years: Requires consulting a healthcare provider

Drink 1 cup of liquid with each dose. Magnesium citrate may be taken as a single daily dose or in divided doses. Pros and cons include:

  • Pros: It's available as a solution and as a powder to be mixed with a liquid, produces bowel movement in half an hour to six hours, and can be used as a bowel prep.

  • Cons: The unused product must be discarded within 24 hours of opening the bottle. It's a more potent saline laxative, causing loose stools, diarrhea, stomach cramps, and risk of high magnesium levels, especially with poor kidney function.

Magnesium Sulfate (Epsom Salts)

Magnesium sulfate, commonly known as Epsom salts, has also been used for constipation. The following includes its typical dosage:

  • Adults and children 12 years and over: 2 to 4 level teaspoons (10 to 20 g) dissolved in 1 cup of water daily

  • Children 6 to 11 years: 1 to 2 level teaspoons (5 to 10 g) dissolved in 1 cup of water daily

  • Children under 6 years: Requires consulting a healthcare provider

Magnesium sulfate can be taken as a single daily dose or in divided doses.

To improve the taste, you may add some lemon juice. Pros and cons include:

  • Pros: It's available as granules, produces bowel movements in half an hour to six hours, and can be used externally as a soaking aid for minor sprains and bruises.

  • Cons: It comes with a risk of high magnesium levels, especially with poor kidney function.

Which Magnesium Is Best for Constipation?

The following magnesium salts are considered saline laxatives:

  • Magnesium oxide

  • Magnesium hydroxide

  • Magnesium citrate

  • Magnesium sulfate

They draw water into the intestines, softening the stool and making it easier to pass.

Studies suggest magnesium citrate is a more potent saline laxative. Besides being used for constipation, magnesium citrate is also used to empty the bowel in preparation for colonoscopy, a procedure used to screen for colon cancer and any abnormalities in the bowel.

Although magnesium oxide is associated with diarrhea, its low absorption rate suggests that it may have less of a tendency to cause high magnesium levels in the body than other forms of magnesium.

Each salt form comes in different formulations, such as tablets, powder, suspension, liquid, and granules, and may have other uses in addition to constipation.

For example, magnesium hydroxide (milk of magnesia) is also used as an antacid.

Therefore, the form of magnesium used for constipation is individualized.

How Long Does Magnesium Take to Start Working?

Magnesium hydroxide, citrate, and sulfate generally produce a bowel movement within 30 minutes to six hours.

Side Effects

Magnesium supplements can cause diarrhea, nausea, and vomiting.

The types of magnesium most commonly reported to cause diarrhea include magnesium carbonate, chloride, gluconate, and oxide.

Symptoms of magnesium toxicity include the following:

Who Should Avoid It?

Avoid magnesium if you're allergic to it or its components (parts). Seek immediate medical attention if you have a severe allergic reaction (itching, hives, shortness of breath).

The kidneys are responsible for regulating magnesium levels in the blood. However, if you have kidney problems, the risk of magnesium buildup increases.

Therefore, people with poor kidney function should avoid magnesium due to an increased risk of heart block or increased magnesium levels in the blood.

Precautions

When taking magnesium, caution should be taken if you:

  • Have kidney disease

  • Have stomach pain, nausea, or vomiting

  • Have a sudden change in bowel habits that lasts more than one week

  • Are on a magnesium or sodium-restricted diet

  • Are pregnant or breastfeeding

  • Are of advanced age

The risk of developing high magnesium levels in the blood increases with decreased kidney function and large daily doses of magnesium supplements.

Guidelines from Japan recommended that blood magnesium concentrations be measured periodically in older adults and people using magnesium oxide for prolonged periods.

Interactions

Magnesium decreases the efficacy of certain medications and supplements, including:

Be sure to space out the time between taking magnesium supplements and antibiotics (doxycycline, ciprofloxacin, and azithromycin) and other medications by at least two hours.

High doses of zinc supplements can interfere with magnesium absorption in the body.

Diuretics or water pills, such as Lasix can increase the loss of magnesium in the urine.

The use of proton-pump inhibitors (acid-reducing drugs) such as Nexium (esomeprazole) or Prevacid (lansoprazole) for more than a year can cause low magnesium levels.

The laxative effect of magnesium oxide is decreased when taken with acid-reducing drugs, such as Pepcid (famotidine) or Prilosec (omeprazole).

The following drugs may increase magnesium levels in the blood:



Explainer

In the United States, the Food and Drug Administration (FDA) does not regulate supplements like prescription drugs. This means some supplement products may not contain what the label says.

When choosing a supplement, look for third-party-tested products and consult a healthcare provider, registered dietitian nutritionist (RDN or RD), or pharmacist.



Strategies for Digestive Health

Approaches recommended to prevent and manage constipation include the following:

  • Engage in regular physical activity

  • Respond to your urge to have a bowel movement

  • Increase your fluid intake

  • Gradually increase your fiber intake (20–35 g of fiber per day in fruits, vegetables, nuts, whole grains, and supplements)

Summary

Maintaining a regular bowel movement is important for digestive health.

Various forms of magnesium, such as magnesium oxide, hydroxide, citrate, and sulfate, are used for constipation due to their ability to draw water into the intestines.

Please consult with your healthcare provider before starting magnesium supplements if you have certain medical conditions, such as kidney problems, or take certain drugs.

Frequently Asked Questions

Which magnesium is best for constipation?

Magnesium oxide, hydroxide, magnesium citrate, and magnesium sulfate are classified as saline laxatives.

Studies comparing the various forms of magnesium among each other are needed to clarify which type of magnesium is best for constipation.

However, magnesium citrate is generally suggested to have a stronger laxative effect than other magnesium preparations.

Is magnesium good for constipation?

Magnesium works for constipation by retaining fluids in the intestines, which softens the stool and makes it easier to pass.

Because magnesium interacts with some medications and should be avoided in people with certain medical conditions, please consult your healthcare provider to determine if a magnesium-based laxative is appropriate.

How much magnesium citrate is used for constipation?

For adults and children 12 years of age and over, the dose is half a bottle to one bottle (10 fluid ounces).

For children six to 11 years of age, the dose is one-third to one-half of a bottle (3 to 5 ounces).

For children under 6 years of age, please consult a healthcare provider.

Be sure to drink 8 ounces of water with each dose (can be taken as a single daily dose or in divided doses).

Read the original article on Verywell Health.