Magnesium Oxide
Magnesium Oxide is used as an antacid to relieve heartburn and indigestion, and as a magnesium supplement.
Magnesium Oxide is an antacid and mineral supplement used to treat acid-related stomach issues, correct magnesium deficiency, and relieve occasional constipation.
Key facts at a glance
- ATC
- A02AA02
- RxNorm
- 6585
- Generic
- Magnesium Oxide
- Class
- atc-a02
- Brands
- Folgard OS, Lactocal, Vitafol-One, Somnicin, Clenpiq, Beelith, Phillips' Cramp-free, Magmilax, Mag-Ox 400, Uro-Mag
- Availability
- otc
- Pregnancy
- B
- Lactation
- safe
- Half-life (h)
- 8
- Onset (min)
- 20
- Duration (h)
- 4
- Routes
- oral
- Forms
- tablet, capsule, chewable tablet, powder, oral suspension
- Regions
- United States, Canada, United Kingdom, Australia, Germany, France, Japan, Brazil
- Monitoring
- serum magnesium, renal function, electrolytes
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 500mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 250mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 400mg daily
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
9 groupspregnancy
first trimesterno adjustment needed
use under healthcare provider supervision; do not exceed recommended daily allowance
routine prenatal care
pregnancy
second trimesterno adjustment needed
continue as prescribed for deficiency or as antacid; follow provider guidance
routine prenatal monitoring
pregnancy
third trimesterno adjustment needed
may be used for magnesium deficiency or as antacid; continue under medical supervision
routine prenatal care and magnesium levels if supplementation
lactation
breastfeedingno adjustment needed
generally safe; magnesium crosses into breastmilk in small amounts
infant monitoring not typically required
geriatric
elderlyreduce dose and monitor renal function
use with caution due to age-related decline in renal function; start with lowest effective dose
monitor serum magnesium and renal function tests periodically
Use with caution and monitor for adverse effects.
pediatric_age
children adolescentsweight-based dosing required
use pediatric formulation; do not exceed recommended weight-based doses
monitor for diarrhea and other gi symptoms
renal_impairment
mild renal impairmentmonitor serum magnesium; may need dose reduction
use with caution; monitor renal function and magnesium levels
check serum magnesium and creatinine regularly
Use with caution and monitor for adverse effects.
renal_impairment
moderate severe renal impairmentsignificant dose reduction or avoid
avoid high doses; contraindicated in severe renal failure without dialysis
Use with caution and monitor for adverse effects.
hepatic_impairment
mild moderate hepatic impairmentno adjustment typically needed
magnesium is not hepatically metabolized; use as indicated
standard monitoring
Statistics and clinical data
Drug class
Magnesium compound used as dietary supplement
Common uses
Therapeutic applications of magnesium oxide
Commonly prescribed since
General prescribing information
Mechanism of action
Pharmacological mechanism
Magnesium Oxide is used to treat symptoms of heartburn, acid indigestion, sour stomach, and gastroesophageal reflux disease (GERD). It also serves as a supplement to prevent or treat low blood magnesium levels and may be used as a short-term laxative for constipation relief.
As an antacid, Magnesium Oxide neutralizes stomach acid (hydrochloric acid) by converting it to water and a magnesium salt. At higher doses, it acts osmotically in the intestines, drawing water into the bowel to soften stool and stimulate intestinal motility, thereby producing a laxative effect.
Take with a full glass of water. Separate administration from other medications by at least 2 hours, as Magnesium Oxide can reduce absorption of antibiotics, thyroid hormones, and bisphosphonates. Common side effects include diarrhea and abdominal cramping. Use cautiously in patients with kidney disease. Do not use as a laxative for more than one week without medical advice. Persistent symptoms may indicate a more serious condition requiring evaluation.
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
WellAlly may earn a referral fee from linked resources at no extra cost to you. Editorial content is never influenced by commercial relationships.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 27, 2026. · Read our editorial policy