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Overview: Magnesium antacids are taken to help relieve indigestion, heartburn, or a sour stomach. You may notice that your poop may be loose, watery, or more frequent when taking a magnesium antacid. Do not take more than the recommended dose. Magnesium antacids come in many different salts and forms. Ask your health care provider if you are not sure which product to take. Tell your health care provider about all of your health conditions and any medicines you take.

Uses

What are magnesium antacids used for?

Magnesium antacids are commonly taken to help relieve the following symptoms. 

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

How do magnesium antacids work (mechanism of action)?

Magnesium antacids neutralize stomach acid. This helps reduce indigestion, heartburn, or sour stomach.

What forms of magnesium are typically used as antacids for heartburn, sour stomach, or acid indigestion?

  • Magnesium aluminosilicates
  • Magnesium carbonate
  • Magnesium glycinate
  • Magnesium hydroxide
  • Magnesium oxide
  • Magnesium trisilicate

Magnesium antacids are commonly found in products that also contain other ingredients, such as aluminum hydroxide, calcium carbonate, and/or simethicone.

Some magnesium forms are used as laxatives or supplements. See Magnesium Laxatives or Magnesium Supplements for more information.

How should I store magnesium antacids?

Storage requirements may vary among magnesium antacids. Magnesium antacids should generally be stored at room temperature, between 68 F and 77 F (20 C and 25 C). Avoid freezing. Storage requirements for some magnesium antacids may not be provided with the product packaging. If you are not sure how to store your magnesium antacid, ask your pharmacist.

Side Effects

What are the most common side effects of magnesium antacids?

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

  • Stomach cramps
  • Diarrhea
  • Nausea

There may be other side effects of magnesium antacids 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 antacids?

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

Severe Allergic Reactions. Magnesium antacids may cause allergic reactions, which can be serious. Stop taking magnesium antacids 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 antacids?

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

  • Magnesium
  • Milk of magnesia (MOM)
  • Any of the ingredients in the specific product

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

What should I know about magnesium antacids before using it?

Magnesium antacids come in many different salts and dosage forms. Some of these may work better for you than others. Some may cause fewer side effects than others. If you are not sure which magnesium antacid you should take, talk to your health care provider.

Read and follow the instructions for the product you have and make sure you understand how to take it properly. Do not take more than the recommended dose. Do not take the maximum dose for more than 2 weeks unless your health care provider tells you to. Taking too much magnesium can cause side effects.

Keep magnesium antacids out of the reach of children.

Magnesium antacids may have a laxative effect. This means your poop may be loose, watery, or more frequent. This may be more common if you are taking a magnesium antacid often or at high doses. Talk to your health care provider if you have concerns.

If you are taking a liquid magnesium antacid, check the label to see if you need to shake it. Some liquid magnesium antacids need to be shaken well before you measure your dose. Use an accurate measuring device to measure your dose of liquid magnesium antacid. 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.

Magnesium antacids may affect how other medicines work. You may need to take magnesium antacids at a different time than other medicines. Your health care provider can let you know when to take each medicine.

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

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 antacids 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.

  • Nausea or vomiting
  • Pain in your lower stomach area
  • A sudden change in your pooping habits that has lasted for 2 weeks or longer
  • Kidney problems
  • Electrolyte problems, such as low or high levels of magnesium, potassium, or sodium

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 antacid if you have dietary restrictions.

Other Medicines and Supplements. Magnesium antacids may interact with other medicines and supplements. Before taking magnesium antacids, 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 antacid 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 antacid while breastfeeding.

Interactions

Do magnesium antacids interact with foods or drinks?

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

It is unknown if drinking alcohol will affect magnesium antacids.

Do magnesium antacids 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 antacids.

  • 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 antacids 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 antacids. 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 antacids?

If you or someone else has taken too much magnesium antacids, 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 antacids?

Magnesium antacids are meant to be taken only when needed. Take them according to the product directions or as your health care provider recommends. Do not take double or extra doses.