What Is Magnesium Oxide?

Can magnesium oxide help with some health conditions?

Magnesium oxide is a magnesium salt form. While most people get magnesium from food, sometimes supplementation is needed. It is one of a few types of magnesium supplements and is also an ingredient in some over-the-counter (OTC) medications.

Magnesium oxide is most commonly used in treating low magnesium levels and constipation. It has also been studied for its effects on blood pressure, type 2 diabetes, and migraines.

Available without a prescription, magnesium oxide is generally safe, although it may cause stomach aches and diarrhea in some. The recommended daily magnesium intake from all sources is between 310 milligrams (mg) and 400 milligrams for younger adults and between 320 milligrams and 420 milligrams for older adults.

This article discusses the purported uses of magnesium oxide, including the possible side effects, risks, interactions, and how it differs from other forms of magnesium (such as magnesium citrate).

Supplement Facts

  • Active ingredient(s): Magnesium oxide
  • Alternate name(s): Magnesia
  • Legal status: Available over-the-counter in supplements and some laxatives
  • Suggested dose: Between 310 milligrams and 420 milligrams in adults, based on age
  • Safety considerations: Generally safe, but may cause stomach aches and diarrhea

Uses of Magnesium Oxide

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian nutritionist, pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent a disease.

Magnesium oxide is a magnesium mineral supplement that consists of magnesium and oxygen ions. There are other types of magnesium supplements as well.

Magnesium Deficiency

Magnesium deficiency in the general healthy population is uncommon, but low intakes (e.g., older adults) or losses due to health conditions (e.g., gastrointestinal diseases, type 2 diabetes, alcohol abuse) may lead to a magnesium deficiency.

Early signs of a magnesium deficiency include:

  • Loss of appetite
  • Nausea or vomiting
  • Fatigue
  • Weakness

When deficiency worsens, symptoms can progress to:

  • Numbness or tingling
  • Muscle cramps
  • Seizures
  • Abnormal heart rate

Note that you can receive magnesium through diet and supplements. Before starting any supplements, please discuss them with your healthcare provider.


Magnesium can be a primary ingredient in some laxatives (e.g., Philips' Milk of Magnesium).

Magnesium oxide should only be used short-term as a laxative to help with constipation. The supplement has an osmotic effect. It draws water into the intestines to soften stool, making it easier to pass.

One randomized, double-blind, placebo-controlled trial evaluated the effects of magnesium oxide in adults with chronic mild-to-moderate constipation. Seventeen individuals took magnesium oxide for 28 days and 17 took a placebo.

At the end of the study, magnesium oxide significantly improved overall symptoms, including spontaneous bowel movement, stool form, colonic transit time, and abdominal symptoms compared with the placebo.

If you have constipation, talk to your healthcare provider about the most appropriate treatment option for you. Call your healthcare provider if your constipation does not improve or worsens.

Magnesium Oxide
Bruce Gifford/Getty Images.

Blood Pressure and Risk of Stroke

Magnesium oxide has also been researched to reduce high blood pressure (hypertension) and lower the risk of stroke.

A review that looked at seven prospective studies found diets high in magnesium can reduce diastolic blood pressure and reduce the risk of stroke, especially ischemic strokes. An ischemic stroke occurs when the artery to the brain is blocked. It is typically caused by high blood pressure.

Another systematic review of 49 studies involving oral magnesium supplementation and blood pressure effects showed promising but conflicting results. The review concluded with the following findings:

  • No significant blood-pressure-lowering effect was found with magnesium supplementation in people with controlled hypertension and healthy blood pressure numbers
  • Oral magnesium at 240 milligrams (mg) per day safely lowered blood pressure in people with uncontrolled hypertension who also take blood pressure medications.
  • Oral magnesium at 600 milligrams per day was needed to lower blood pressure in people with untreated hypertension.

Type 2 Diabetes

Diets high in magnesium have been associated with a lower risk of type 2 diabetes.

One long-term meta-analysis of seven studies including 286,668 people found that 100 milligrams per day in total magnesium intake significantly lowered the risk of diabetes.

Another meta-analysis of 13 studies demonstrated a dose-dependent association between magnesium intake and type 2 diabetes risk. However, this was only statistically significant in individuals who were overweight.

However, very few short-term clinical trials have been done on its effects on controlling type 2 diabetes.

Note that the American Diabetes Association states there is not enough research to support using magnesium supplements to improve blood glucose in people with type 2 diabetes.

If you have diabetes, please consult your healthcare provider before starting magnesium oxide supplementation.


Magnesium oxide supplementation may reduce the number and intensity of migraines.

A randomized, double-blind crossover study showed that taking 500 milligrams of magnesium oxide appeared to be as effective as valproate sodium in preventing migraine attacks. Sixty-three people in the study took either magnesium oxide or valproate sodium.

The American Academy of Neurology and the American Headache Society concluded that magnesium therapy is "probably effective" for migraine prevention. However, the typical dose of magnesium used for migraine prevention is more significant than magnesium's tolerable upper limit (UL). Therefore, it should be used under the supervision of a healthcare provider. Still, research is limited.

Please discuss the use of magnesium oxide supplements with your healthcare provider before taking them if you have migraines.

What Are the Side Effects of Magnesium Oxide?

Consuming a supplement like magnesium oxide may have potential side effects. These side effects may be mild or severe.

Upset stomach and diarrhea are the most common side effects of magnesium oxide. Taking magnesium oxide with food can reduce stomach troubles. If side effects are persistent or worsen, it is best to talk to your healthcare provider. 

Severe allergic reactions to magnesium oxide are rare. However, seek immediate medical help if you develop:


People with kidney problems should talk to their healthcare providers before starting magnesium oxide supplements.

In addition, pregnant and lactating individuals and children should avoid magnesium oxide supplements as the risks are unknown.

Dosage: How Much Magnesium Oxide Should I Take?

Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.

The following is the Recommended Dietary Allowance (RDA) for magnesium:

  • Young adults (19 to 30 years): 400 milligrams per day for males and 310 milligrams per day for females
  • Adults over 30: 420 milligrams per day for males and 320 milligrams per day for females

Magnesium oxide supplements should be taken by mouth with meals to reduce stomach upset. Do not crush or chew the supplements; doing so will increase the risk of side effects. If taken in liquid form, shake and measure the proper dose according to the instructions on the supplement's label.

Discuss your consumption of magnesium oxide with a healthcare provider to determine the appropriate amount for your needs.

What Happens If I Take Too Much Magnesium Oxide?

It is possible to take too much magnesium oxide. Large doses of magnesium oxide can cause magnesium toxicity. This is more likely in people with kidney problems.

Taking too much magnesium oxide may result in:

  • Gastrointestinal problems, such as nausea, diarrhea, stomach cramps, and vomiting
  • Lethargy
  • Muscle weakness
  • Heart-related symptoms such as an irregular heartbeat or low blood pressure
  • Trouble breathing

If you have any of these symptoms after taking magnesium oxide, seek medical care at once. 


Magnesium oxide may prevent the absorption of several medications. Before starting magnesium oxide supplementation, please discuss the prescription and OTC medications, vitamins, or herbal supplements you take with your healthcare provider.

Magnesium oxide may reduce how well the Parkinson's disease treatment Sinemet (levodopa and carbidopa) works. However, more studies are needed to confirm this interaction.

Other medications that can interact with magnesium oxide include:

Magnesium oxide may interact with the following supplements:

  • Iron
  • Calcium polycarbophil
  • Calcium supplements (in high dosages)

Other interactions may occur. Before starting magnesium oxide, ask your healthcare provider or pharmacist for a complete list of potential drug, supplement, and food interactions.

Read the Product Label

Carefully read the ingredient list and nutrition facts panel of a supplement to know which ingredients and how much of each ingredient is included. Please review this supplement label with your healthcare provider to discuss any potential interactions with foods, other supplements, and medications.

Frequently Asked Questions

  • What is the difference between magnesium oxide and other forms of magnesium?

    Magnesium oxide is a type of magnesium that also contains oxygen. Other forms of magnesium supplements include:

    • Magnesium chloride
    • Magnesium citrate
    • Magnesium glycinate
    • Magnesium lactate
    • Magnesium malate
    • Magnesium orotate
    • Magnesium sulfate
    • Magnesium L-threonate

    Of the different types, magnesium citrate is among the most easily absorbed in the body and one of the most popular forms found on drugstore shelves.

  • What is the best source of magnesium?

    The best way to get magnesium is through your diet and eating a variety of magnesium-rich foods, such as spinach, legumes, nuts, seeds, and whole grains.

    Supplements are an option for maintaining magnesium levels in people whose levels remain low despite diet changes. Please talk to your healthcare provider before starting a magnesium oxide supplement.

  • How do I know if I should take a magnesium oxide supplement

    A healthcare provider can assist you in determining if magnesium oxide supplements are needed for maintaining and/or increasing magnesium. A blood test is usually used to check the level of magnesium in your blood.

    Anyone who thinks their magnesium is low should talk to their healthcare provider before starting a supplement.

Sources of Magnesium Oxide

Magnesium is found in many plant and animal foods and beverages, including green leafy vegetables (spinach), legumes, nuts, seeds, and whole grains. Usually, foods that are higher in fiber are rich in magnesium.

Magnesium oxide supplements are available OTC without a prescription. Magnesium oxide is sold under several brand names. Your healthcare provider or pharmacist can advise you on which brand might fit your unique situation and overall health.

Before picking up a magnesium supplement, it is a good idea to have your magnesium levels checked by a healthcare provider. There is no way to know if the symptoms you might be experiencing are related to a magnesium deficiency, another deficiency, or an illness. You should always disclose all health conditions and medications to avoid interactions and adverse reactions.


Getting enough magnesium is important for good health. Without it, the body cannot function properly. Eating magnesium-rich foods usually does the trick. These include green leafy vegetables, legumes, nuts, seeds, and whole grains.

Magnesium oxide can also be found in some laxatives and supplements. Although your daily dose of magnesium is crucial, consuming magnesium in excessive quantities can be detrimental to your health. Therefore, it is always important to consult your healthcare provider before starting magnesium supplementation.

Talk to your healthcare provider if you suspect you have low magnesium levels. The most common symptoms of deficiency are muscle cramping, fatigue, depression, and irritability.

13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Alena Clark, PhD
Alena Clark, PhD, is a registered dietitian and experienced nutrition and health educator

Originally written by Cathy Wong
Cathy Wong

Cathy Wong is a nutritionist and wellness expert. Her work is regularly featured in media such as First For Women, Woman's World, and Natural Health.

Learn about our editorial process