Parkview Health Logo

A guide to magnesium

Last Modified: July 01, 2024

Family Medicine, Nutrition & Recipes

dietary sources of magnesium

This post was written by Curt Stump, PharmD, BCPS, Parkview Health.

Research on dietary habits in the United States consistently indicates that many Americans do not meet the recommended daily magnesium intake. Current data from the National Institutes of Health Office of Dietary Supplements found that 48% of Americans of all ages ingest less magnesium from food and beverages than their estimated average requirements. In this post, we will discuss the importance of magnesium, how to get it, signs of deficiency and options for over-the-counter magnesium products.

What is magnesium?

Magnesium is one of many nutrients your body needs to stay healthy. It plays a crucial role in regulating blood pressure, helping muscles move and contract, controlling blood sugar and more. This mineral naturally occurs in green leafy vegetables, nuts and seeds, whole grains and milk. Fortified foods, such as cereals, also contain added magnesium. Even tap, mineral and bottled water contain traces of magnesium; however, the exact amount varies by brand. The best way to know exactly how much magnesium your food contains is to read the nutrition facts label.

Magnesium is also available in various over-the-counter products, including dietary supplements, multivitamins and medications used to treat indigestion and heartburn. It is imperative to note that the various magnesium products may have different active ingredients, uses, warnings and directions. Always read nutrition and drug labels carefully and ask your primary care provider or pharmacist if you have any questions.

How much magnesium do I need?

The amount of magnesium an individual needs daily depends on age and sex. The table below provides average daily recommendations for adult men and women. These values include magnesium from food, beverages, dietary supplements and medications. In healthy individuals, any excess magnesium consumed is excreted from the body in the urine.

*Includes magnesium from food, beverages, dietary supplements and medications.

Most people are advised to obtain daily magnesium primarily through food and beverages. However, for individuals who cannot meet their suggested amount through diet alone, there are over-the-counter dietary supplements and medications that contain magnesium.

The amount of magnesium consumed from dietary supplements and medications should not exceed 350 mg, which is the maximum daily intake considered safe for most adults unless recommended by a physician. Higher doses of magnesium from these products can often result in diarrhea, nausea and abdominal cramping.

What are the signs of magnesium deficiency?

Short-term, low dietary magnesium intake is unlikely to cause symptoms of magnesium deficiency. When healthy individuals have low magnesium intake, the kidneys help conserve the body's magnesium by reducing the amount that is lost in urine. However, low intake for a prolonged period, certain medical conditions and even some medications can lead to magnesium deficiency.

Medical conditions that may cause low magnesium include:

Medications that can contribute to low magnesium:

  • Diuretics (water pills) such as furosemide, hydrochlorothiazide or spironolactone

  • Proton pump inhibitors such as omeprazole

Early signs of a magnesium deficiency include:

Shakiness and muscle cramps may be more severe indications of magnesium deficiency. Talk to your doctor if you believe you are experiencing these symptoms. 

Which magnesium products should I use?

If you cannot meet your recommended amount of daily magnesium through your diet alone or are considering using magnesium products for another reason, discuss your options with your primary care physician. They may recommend specific over-the-counter magnesium products that best match your goal.

The table below breaks down some of the over-the-counter magnesium products that may be attainable at your local pharmacy. Keep in mind this is not an all-encompassing list of the available products. Manufacturers also market many of these products used as antacids or laxatives as dietary supplements. Personal usage may differ from the common uses listed here. 

Is it safe to take multiple forms of magnesium for coexisting conditions such as anxiety, constipation and sleep issues?

Remember that the total amount of magnesium consumed from ALL dietary sources, supplements and medications should not exceed 350 mg to prevent undesirable side effects. If you take multiple products that contain magnesium, it is crucial to review the labels of each product to see how much magnesium each serving or dose contains. Calculate the daily total amount and compare that to the recommended maximum dosage. Let's look at this magnesium oxide label as an example. This magnesium product can be used as a supplement or medication for heartburn and indigestion.

The label will provide the exact number we are looking for under Supplement Facts if it is a dietary supplement. In this case, the dosage listed is 241.3 mg per tablet. Additionally, looking under Drug Facts and Other Information will give you this information since this product has multiple uses. If you plan to use magnesium hydroxide as a laxative, look under Drug Facts and Additional Information to see how much magnesium each dose contains. In this instance, every 15 mL contains 500 mg of magnesium, so an adult dose of 30-60 mL would contain 1,000-2,000 mg of magnesium. The specific wording to watch out for on the label is the "milligrams (mg) of magnesium" or "elemental magnesium," and NOT the "milligrams (mg) of magnesium hydroxide," as in this example.

You may have noticed that the above adult dose exceeds the recommended maximum of 350 mg. Drug and supplement labels can be ambiguous, so it is important to talk to your doctor and local retail pharmacist. They will have a greater understanding of your medical history and unique needs.

To put it simply, very little magnesium is absorbed by your body after a dose of magnesium hydroxide (only about 4%) due to the laxative effect of the product. This higher dosage of magnesium helps your body produce a bowel movement. It also explains some common side effects, such as diarrhea, nausea and abdominal cramping.

What about topical magnesium oil?

Topical magnesium oil or magnesium oil spray has gained recent popularity on social media because of its potential benefits. The magnesium concentration in these products tends to vary depending on the brand, and like dietary supplements, they do not have to undergo rigorous clinical trials to prove effectiveness for any specific use.

Although the efficacy of this application method is still being researched, the idea is that the magnesium oil will be absorbed when massaged into the skin. Common areas of application include the arms, legs and feet.

The proposed advantage of topical magnesium over oral magnesium supplements is that it bypasses the digestive system. Topical application may be more suitable for patients who experience intolerable diarrhea or abdominal cramping from oral supplements. However, it can cause skin irritation, tingling or itching for some patients. It's best to test a small area first and never apply the product to broken skin.

Keep in mind that the quantity of magnesium absorbed following the application of this product is unknown, so we are unable to account for it in relation to the daily maximum dose.

Final thoughts

While magnesium supplements can be beneficial for individuals unable to obtain their required daily intake, it's important to be mindful of the numerous forms of magnesium and their various uses. Always review supplement and medication product labels carefully and consult your pharmacist for any questions or concerns.

Parkview Outpatient Pharmacies are committed to exceptional service and work directly with your doctor to ensure medication appropriateness and safety. Contact your preferred Parkview outpatient pharmacy and our staff will gladly assist you with questions or prescription transfers.



Related Blog Posts

View all posts