Magnesium hydroxide

By Medically reviewed by hellodoktor

Generic Name: Magnesium hydroxide Brand Name(s): Generics only. No brands available.


What is magnesium hydroxide used for?

Magnesium hydroxide is an antacid. It is commonly used for treating acid indigestion, heartburn, sour stomach, and constipation. It may also be used for other conditions as determined by your doctor.

How should I take magnesium hydroxide?

Take magnesium hydroxide by mouth with or without food. Follow with a full glass (8 oz/240 mL) of water or other liquid.

Ask your health care provider any questions you may have about how to use magnesium hydroxide.

How do I store magnesium hydroxide?

Magnesium hydroxide is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store magnesium hydroxide in the bathroom or the freezer. There may be different brands of magnesium hydroxide that may have different storage needs. It is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush magnesium hydroxide down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Precautions & warnings

What should I know before using magnesium hydroxide?

Before using this drug, tell your doctor if:

  • You are pregnant or breastfeeding. This is because, while you are expecting or feeding a baby, you should only take medicines on the recommendation of a doctor.
  • You are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • You have allergy with any of active or inactive ingredients of magnesium hydroxide or other medications.
  • You have any other illnesses, disorders, or medical conditions.

Magnesium hydroxide usually causes a bowel movement within 30 minutes to 6 hours of using it. If you do not have a bowel movement after using magnesium hydroxide, contact your doctor.

Do not take more than the recommended dose or use the maximum dose for longer than 1 week without checking with your doctor.

If your symptoms do not get better within 1 week or if they get worse, check with your doctor.

Magnesium hydroxide should not be used in children younger than 12 years old; safety and effectiveness in these children have not been confirmed.

Is it safe during pregnancy or breastfeeding?

There are no adequate studies in women for determining risk when using this Magnesium hydroxide during pregnancy or while breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking this Magnesium hydroxide. This Magnesium hydroxide is pregnancy risk category N, according to the US Food and Drug Administration (FDA).

FDA pregnancy risk category reference below:

  • A=No risk
  • B=No risk in some studies
  • C=There may be some risk
  • D=Positive evidence of risk
  • X=Contraindicated
  • N=Unknown

Side effects

What side effects can occur from magnesium hydroxide?

Check with your doctor if any of these most common side effects persist or become bothersome:

  • Diarrhea

Seek medical attention right away if any of these severe side effects occur:

  • Rash
  • Hives
  • Itching
  • Difficulty breathing
  • Tightness in the chest
  • Swelling of the mouth, face, lips, or tongue
  • Loss of appetite
  • Muscle weakness
  • Nausea
  • Slow reflexes
  • Vomiting

Not everyone experiences these side effects. There may be some side effects not listed above. If you have any concerns about a side-effect, please consult your doctor or pharmacist.


What drugs may interact with magnesium hydroxide?

Magnesium hydroxide may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval.

Products may interact with your drug, including:

  • Anticoagulants (e.g., warfarin) because the risk of their side effects may be increased by magnesium hydroxide.
  • Azole antifungals (e.g., ketoconazole), bisphosphonates (e.g., alendronate), cation exchange resins (e.g., sodium polystyrene sulfonate), cephalosporins (e.g., cephalexin), mycophenolate, penicillamine, quinolone antibiotics (e.g., ciprofloxacin), or tetracyclines (e.g., doxycycline) because their effectiveness may be decreased by magnesium hydroxide.

Does food or alcohol interact with magnesium hydroxide?

Magnesium hydroxide may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with magnesium hydroxide?

Magnesium hydroxide may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have.

These health conditions may include:

  • Appendicitis
  • Stomach pain
  • A blockage of your bowels
  • Nausea
  • Vomiting
  • Diarrhea
  • Kidney problems
  • Rectal bleeding of unknown cause
  • A bowel surgery


The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using magnesium hydroxide.

What is the dose of magnesium hydroxide for an adult?

Chewable tablet: 2-4 tablets PO q4hr; no more than 4 doses per 24-hour period.

What is the dose of magnesium hydroxide for a child?

<12 years: Not recommended.

≥12 years: 2-4 tablets PO q4hr; no more than 4 doses per 24-hour period.

How is magnesium hydroxide available?

Magnesium hydroxide is available in the following dosage forms and strengths:

  • Tablet 311mg or 400mg

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to your nearest emergency room.

What should I do if I miss a dose?

If you miss a dose of magnesium hydroxide, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Review Date: May 14, 2017 | Last Modified: September 13, 2019

You might also like