What to Know About Magnesium Oxide

Magnesium oxide is a form of magnesium salt. Most people get magnesium from food, but supplementation is sometimes needed. 

Magnesium oxide is one of a few types of magnesium supplements you can get without a prescription. It is also an ingredient in some over-the-counter (OTC) medications. It is most commonly used to treat low magnesium levels and constipation. It has also been studied for its effects on blood pressure, type 2 diabetes, and migraines.

Magnesium oxide is generally safe, although it may cause stomach aches and diarrhea. 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 possible uses of magnesium oxide, including the side effects, risks, interactions, and how it differs from other forms of magnesium (such as magnesium citrate).

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 has magnesium and oxygen ions. 

Magnesium Deficiency

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

Early signs of a magnesium deficiency include:

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

When the deficiency gets worse, symptoms can include:

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

You can get magnesium through your diet and supplements. Before starting any supplements, please discuss them with your healthcare provider.

Constipation

Magnesium is an ingredient in some laxatives (e.g., Philips' Milk of Magnesium). The supplement draws water into the intestines to soften stool, making it easier to pass (osmotic effect).

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

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

Magnesium oxide should only be used as a short-term treatment for constipation. If you have constipation, talk to your healthcare provider about the best treatment for you. Call your provider if your constipation does not get better or gets worse after trying magnesium oxide.

Blood Pressure and Risk of Stroke

Magnesium oxide might help reduce high blood pressure (hypertension) and lower the risk of stroke.

A review that looked at seven prospective studies found that diets high in magnesium can reduce diastolic blood pressure and may reduce the risk of stroke (especially ischemic strokes, which happen when an artery in the brain is blocked. This kind of stroke is often caused by high blood pressure). 

Another systematic review of 49 studies on oral magnesium supplementation and blood pressure showed promising but conflicting results:

• 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 people who were overweight.

However, very few short-term clinical trials have been done on magnesium oxide’s effects on controlling type 2 diabetes. The American Diabetes Association (ADA) 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, talk to your provider before starting magnesium oxide supplementation.

Migraines

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, but research is limited.

It’s also important to note that the typical dose of magnesium used for migraine prevention is higher than magnesium's tolerable upper limit (UL). Therefore, it should only be used under the supervision of a healthcare provider.

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

How It Compares to Other Forms of Magnesium

Other types of magnesium supplements include:

• Magnesium chloride. This form of magnesium supplement is often used in topical products, like skin creams. It's better absorbed by the body than magnesium oxide.
• Magnesium citrate. This form of magnesium supplement is one of the most widely used. It's one of the best forms of magnesium absorbed by the body. It can have similar uses to magnesium oxide, including as a laxative.
• Magnesium glycinate. This form of magnesium is very helpful in fixing a deficiency because the body absorbs it well, and it is less likely to cause diarrhea than magnesium oxide.
• Magnesium lactate. This form of magnesium is bound with lactic acid, which your muscles make when they are working hard. It's more absorbable than magnesium oxide and does not usually cause diarrhea. Sometimes, this form of magnesium is added to foods and drinks to help balance their acidity.
• Magnesium malate. This form of magnesium is absorbed well by the body and some people claim that it helps with whole-body symptoms like fatigue and muscle pain.
• Magnesium orotate. This form of magnesium has orotic acid, which helps the magnesium get into the body's cells. It can be used as a supplement to help with deficiencies but is not as popular as other forms of magnesium, and may not be safe at higher doses.
• Magnesium sulfate. This form of magnesium is commonly known as Epsom salt, which some people use to make baths that are soothing for sore muscles. It's generally not the preferred choice for trying to correct a magnesium deficiency because it can be dangerous if you take too much.
• Magnesium L-threonate. This form of magnesium is combined with threonic acid, which comes from vitamin C. It can be used to help with a deficiency and may have some other health benefits as well, such as for immune function.
  

What Are the Side Effects of Magnesium Oxide?

Consuming a supplement like magnesium oxide may have 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 often prevent these side effects. If side effects do not get better or are getting worse, 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:

• Rash
• Itching
• Swelling
• Severe dizziness
• Irregular heartbeat
• Vomiting
• Trouble breathing

Precautions

People with kidney problems should ask their providers before starting magnesium oxide supplements. In addition, pregnant and lactating people, as well as children, should avoid magnesium oxide supplements because the risks to these groups are unknown.

Dosage: How Much Magnesium Oxide Should I Take?

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 the chances of stomach upset. Do not crush or chew the supplements, as consuming them this way can 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 use of magnesium oxide with your provider to find out the safest and most effective amount to take 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, but this is more likely in people with kidney problems.

Taking too much magnesium oxide may cause:

• Gastrointestinal symptoms (e.g., nausea, diarrhea, stomach cramps, and vomiting)
• Lethargy
• Muscle weakness
• Heart-related symptoms (e.g., irregular heartbeat or low blood pressure)
• Trouble breathing

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

Interactions

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 that you take with your healthcare provider.

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

Other medications that can interact with magnesium oxide include:

• Bisphosphonates such as Fosamax or Binosto (alendronate) (take magnesium-containing supplements at least 2 hours from when you take bisphosphonates)
• Antibiotics such as tetracyclines and quinolones (take antibiotics at least two hours before or 4 to 6 hours after a magnesium supplement)
• Diuretics such as Lasix (furosemide), Bumex (bumetanide), and Microzide (hydrochlorothiazide)
• Proton pump inhibitors such as Nexium (esomeprazole magnesium) and Prevacid (Iansoprazole)
• Neurontin (gabapentin)
• Lanoxin (digoxin)
• Celebrex (celecoxib)
• Crestor (rosuvastatin)

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.

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 starting a magnesium supplement, it is a good idea to have your magnesium levels checked by your provider. There is no way to know if the symptoms you are having are related to a magnesium deficiency, another nutritional deficiency, or an illness. You should tell your provider about any health conditions you have and all medications you’re taking to avoid interactions or adverse reactions.

Summary

Magnesium oxide is a type of magnesium. It’s often an ingredient in laxatives and supplements. 

Getting enough magnesium is important for good health. Without it, the body cannot function properly. Eating magnesium-rich foods, like green leafy vegetables, legumes, nuts, seeds, and whole grains, is usually enough to get the magnesium you need. 

It’s important to make sure you get enough magnesium without getting too much. You should always talk to your provider before starting any supplement. If you think you have low magnesium levels, ask your provider to check them.