Magnesium Oxide

What Is Magnesium Oxide and How Does It Work?

Magnesium oxide is an over-the-counter mineral effective as treatment for constipation, indigestion, magnesium deficiency, high blood pressure during pregnancy (pre-eclampsia and eclampsia), irregular heartbeat, asthma, pain caused by nerve damage associated with cancer, cerebral palsy, chronic fatigue syndrome, chronic obstructive pulmonary disease (COPD), cluster headache, colon and rectal cancer, chest pain (angina) due to clogged arteries, cystic fibrosis, diabetes, fibromyalgia, hearing loss, high cholesterol, metabolic syndrome, diseases of heart valves (mitral valve prolapse), weak bones (osteoporosis), pain after hysterectomy, pain after surgery, premenstrual syndrome (PMS), and chest pain due to blood vessel spasms (vasopastic angina).

  • Magnesium is a mineral that is important for normal bone structure in the body. People get magnesium from their diet, but sometimes magnesium supplements are needed if magnesium levels are too low. Dietary intake of magnesium may be low, particularly among women. Magnesium deficiency is also not uncommon amount African Americans and the elderly. Low magnesium levels in the body have been linked to diseases such as osteoporosis, high blood pressure, clogged arteries, hereditary heard disease, diabetes, and stroke.
  • Magnesium oxide is available under the following different brand names: Mag-Ox 400, Uro-Mag, and Mag-Caps.

What Are Dosages of Magnesium Oxide?

Dosages of Magnesium Oxide:

Adults and Pediatric Dosage:


  • 140 mg (equivalent to 84.5 mg [6.93 milliequivalent] elemental magnesium)


  • 400 mg (equivalent to 240 mg [20 milliequivalent] elemental magnesium)

Dosage Considerations – Should be Given as Follows:

Adult recommended daily intake (elemental magnesium)


  • 19-30 years: 310 mg/day orally
  • 19-30 years (pregnant): 350 mg/day orally
  • Over 31 years: 320 mg/day orally
  • Over 31 years (pregnant): 360 mg/day orally


  • 19-30 years: 400 mg/day orally
  • Over 31 years: 420 mg/day orally

Pediatric, recommended daily intake (elemental magnesium):

  • Children 1-3 years: 80 mg/day orally
  • Children 4-8 years: 130 mg/day orally
  • Children 9-13 tears: 240 mg/day orally
  • Children 14-18 years:
    • Females: 360 mg/day orally
    • Pregnant females: 400 mg/day orally
    • Males: 410 mg/day orally

Magnesium Supplementation

  • Tablet (Mag-Ox): 1-2 tablets orally once daily
  • Capsule (Uro-Mag): 1-5 capsules orally once daily


  • Tablet (Mag-Ox): 1 tablet orally once daily or every 12 hours; not to exceed 2 tablets/day

Renal Impairment

Adult and pediatric:

  • Creatinine clearance under 30 ml/min: caution, monitor for high levels of magnesium in the blood


Adult and pediatric:

  • Take with food

What Are Side Effects Associated with Using Magnesium Oxide?

Common side effects of Magnesium Oxide include:

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Magnesium Oxide?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Benzyl alcohol has no known severe interactions with other drugs.
  • Serious interactions of magnesium oxide include:
  • Magnesium oxide has moderate interactions with at least 23 different drugs.
  • Magnesium oxide has minor interactions with at least 43 different drugs.

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more information about this medicine.

What Are Warnings and Precautions for Magnesium Oxide?


  • This medication contains magnesium oxide. Do not take Mag-Ox 400, Uro-Mag, or Mag-Caps if you are allergic to magnesium oxide or any ingredients contained in this drug.
  • Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.


  • Hypersensitivity

Effects of Drug Abuse

  • No information available

Short-Term Effects

  • See "What Are Side Effects Associated with Using Magnesium Oxide?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Magnesium Oxide?"


  • Normal serum magnesium approximately 1.5-2.5 mg/dL
  • Laxative effect
  • Magnesium supplementation may exacerbate
  • Caution with renal impairment
  • auction with myasthenia gravis or other neuromuscular diseases

Pregnancy and Lactation

  • The use of magnesium oxide during pregnancy is generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk. 350-400 mg/day elemental magnesium is recommended during pregnancy.
  • Magnesium oxide is distributed in breast milk; 310-360 mg/day elemental magnesium is recommended during breastfeeding.
Medscape. Magnesium Oxide.
RxList. Magnesium Supplements.

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