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Overview: Magnesium supplements are taken to increase magnesium levels. Common side effects include nausea, diarrhea, or stomach cramps. Serious side effects are rare, unless you take too much. It is possible to get too much magnesium from supplements. So it is important not to take more than the amount recommended on the product label or by your health care provider. Magnesium supplements come in many different salts and forms. Ask your health care provider if you are not sure whether you need a magnesium supplement or which one to take.

Uses

What are magnesium supplements used for?

Magnesium supplements are commonly taken as a dietary supplement to increase your magnesium levels. 

Magnesium supplements may also be taken for other conditions as determined by your health care provider.

How do magnesium supplements work (mechanism of action)?

Magnesium supplements work by increasing your body’s magnesium levels. 

Magnesium is a mineral. Your body uses magnesium for many important body functions related to your muscles, heart, nerves, blood sugar, and blood pressure. Magnesium is also involved in making proteins, bones, and DNA. The amount of magnesium you should get every day is known as the recommended dietary allowance (RDA). How much magnesium you need depends on your age, sex, and whether you are pregnant or breastfeeding. If you are not sure, ask your health care provider.

What forms of magnesium are typically used as supplements?

  • Magnesium aspartate
  • Magnesium citrate
  • Magnesium chloride
  • Magnesium gluconate
  • Magnesium glycinate
  • Magnesium L-threonate
  • Magnesium lactate
  • Magnesium oxide
  • Magnesium sulfate

Some magnesium forms are used as antacids or laxatives. See Magnesium Antacids or Magnesium Laxatives for more information.

How should I store magnesium supplements?

Storage requirements may vary among magnesium supplements. Magnesium supplements should generally be stored at room temperature, between 68 F and 77 F (20 C and 25 C). Keep tightly closed and store in a cool, dry place. Storage requirements for some magnesium supplements may not be provided with the product packaging. If you are not sure how to store your magnesium supplement, ask your pharmacist.

Side Effects

What are the most common side effects of magnesium supplements?

The most common side effects of magnesium supplements are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Diarrhea
  • Stomach cramps
  • Nausea

There may be other side effects of magnesium supplements that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of magnesium supplements?

While less common, the most serious side effects of magnesium supplements are described below, along with what to do if they happen.

Severe Allergic Reactions. Magnesium supplements may cause allergic reactions, which can be serious. Stop taking magnesium supplements and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use magnesium supplements?

Allergies to Ingredients. People who are allergic to any of the following should not take magnesium supplements.

  • Magnesium
  • Milk of magnesia
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific magnesium supplement products they stock.

What should I know about magnesium supplements before using them?

Magnesium is found in lots of different foods and drinks. It is uncommon for most people to have a low magnesium level or a deficiency, but certain health conditions or medicines may increase your risk. If you are not sure whether you need a magnesium supplement or which one to take, ask your pharmacist or other health care provider. Tell all of your health care providers if you start taking a magnesium supplement.

Magnesium supplements come in many different salts and dosage forms. Some are better absorbed than others. Some may have more side effects than others. Read and follow the instructions for the product you have and make sure you understand how to take it properly. The label will tell you the amount of magnesium in the supplement, which can vary by product. Do not take more than the recommended dose. Taking too much magnesium can cause side effects.

Keep magnesium supplements out of the reach of children.

Magnesium supplements may have a laxative effect, especially if you take high doses. This means your poop may be loose, watery, or more frequent. Talk to your health care provider if you have concerns.

If you are taking a liquid magnesium supplement, check the label to see if you need to shake it. Some liquid magnesium supplements may need to be shaken well before you measure your dose. Use an accurate measuring device to measure your dose of liquid magnesium supplement. A household spoon is not an accurate measuring device and may cause you to take the wrong dose. Ask your pharmacist what measuring device to use.

Some magnesium supplements should not be chewed, cut, or crushed. Follow the directions on the product label and ask your pharmacist if you are not sure how to take it.

What should I tell my health care provider before using magnesium supplements?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if magnesium supplements are right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

Low-Magnesium Diet. Tell your health care provider if you are on a low-magnesium diet. Your health care provider will let you know if you should take a magnesium supplement if you have dietary restrictions.

Upcoming Surgery. Tell your health care provider if you are taking any dietary supplements before a planned surgery or procedure.

Other Medicines and Supplements. Magnesium supplements may interact with other medicines and supplements. Before taking magnesium supplements, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. Tell your health care provider if you are pregnant or plan to become pregnant. Your health care provider will let you know if you should take a magnesium supplement while you are pregnant or trying to get pregnant.

Breastfeeding. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should take a magnesium supplement while breastfeeding.

Interactions

Do magnesium supplements interact with foods or drinks?

There are no known interactions between magnesium supplements and foods or drinks.

It is unknown if drinking alcohol will affect magnesium supplements. Drinking large amounts of alcohol may increase your risk of having low magnesium levels.

Do magnesium supplements interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking magnesium supplements.

  • A bisphosphonate, such as alendronate (Binosto, Fosamax), ibandronate, or risedronate (Actonel, Atelvia), which is a medicine commonly used for osteoporosis
  • A tetracycline, such as doxycycline, minocycline, omadacycline (Nuzyra), sarecycline (Seysara), or tetracycline, which is a medicine used to treat infections or other conditions
  • A fluoroquinolone, such as ciprofloxacin (Cipro, Cipro XR, Porquin), levofloxacin, moxifloxacin, or ofloxacin, which is a medicine used to treat certain infections 
  • A diuretic, also called a water pill, which is a medicine used to reduce edema (fluid retention) and blood pressure
  • A product containing zinc, which is a supplement that may be used for low zinc levels

Magnesium supplements may affect the absorption of many other medicines. Tell your health care provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with magnesium supplements. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much magnesium supplements?

If you or someone else has taken too much magnesium supplements, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of magnesium supplements?

Take your magnesium supplement as directed on the product label or as your health care provider recommends. If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.