Over-the-counter medication · Mineral Supplement
magnesium oxide
Also sold as Mag-Ox. Mag-Ox treats acid indigestion and upset stomach.
Data updated 2026-05-15
- 39,831
- FDA reportsModerately reported
- 1
- InteractionFew interactions
- <$0.01
- Generic price (NADAC)
What the data shows
magnesium oxide (Mag-Ox) is an over-the-counter Mineral Supplement, reported at a middle-of-the-pack volume (39,831 FDA reports), with 1 documented drug interaction.
Reporting volume reflects how widely a drug is used and studied, not how dangerous it is, a FAERS report documents a temporal association, never proof of cause.
magnesium oxide (Mag-Ox) is an over-the-counter Mineral Supplement. Mag-Ox treats acid indigestion and upset stomach.
Magnesium oxide (Mag-Ox) is a mineral supplement. It helps relieve acid indigestion and upset stomach.
Verify with FDA → · CMS NADAC pricing →
Drug Pricing (NADAC)
Generic Price
<$0.01/unit
Generic Available
Yes (14 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
Mag-Ox treats acid indigestion and upset stomach.
Common side effects
Diarrhea
Key warnings
No specific warnings noted. Always follow your prescriber's instructions.
The sections below are summarized in plain English from magnesium oxide's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.
How It Works
Mag-Ox contains magnesium oxide, which neutralizes stomach acid. This helps to reduce discomfort caused by excess acid. It provides relief from indigestion and upset stomach.
How to Take It
Take one or two Mag-Ox tablets each day. You can take it with or without food. Do not take more than two tablets in a day. Talk to your doctor if you need more.
This is a plain-language summary of magnesium oxide's FDA labeling, not individualized dosing advice. Ask a pharmacist or prescriber before changing how you take this medication.
Pregnancy & Breastfeeding
Talk to your doctor before taking Mag-Ox if you are pregnant or breastfeeding. They can help you weigh the risks and benefits.
This is a plain-language summary of magnesium oxide's FDA labeling, not individualized advice. Ask a pharmacist or prescriber about pregnancy or breastfeeding on this medication.
Missed Dose
If you miss a dose, take it as soon as you remember. Do not take more than two tablets in one day.
This is a plain-language summary of magnesium oxide's FDA labeling, not individualized advice. Ask a pharmacist or prescriber what to do about your specific missed dose.
Storage
Store Mag-Ox at room temperature, between 59° to 86°F (15° to 30°C).
Side Effects (from patient reports)
Based on 39,831 FDA adverse event reports.
Most-reported reactions
Adverse reactions in FAERS for magnesium oxide, by number of reports
- Feeling sick to your stomach
Feeling sick to your stomach
2,795 reports
- Loose or watery stools
Loose or watery stools
2,581 reports
- Feeling tired
Feeling tired
2,418 reports
- Difficulty breathing
Difficulty breathing
2,054 reports
- Lung infection
Lung infection
2,031 reports
- Fever
Fever
1,830 reports
- Throwing up
Throwing up
1,665 reports
- Death
Death
1,601 reports
- Head pain
Head pain
1,598 reports
- Low red blood cell count
Low red blood cell count
1,465 reports
What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.
Reports over time
Adverse-event reports filed for magnesium oxide each year to the FDA Adverse Event Reporting System (FAERS).
Year-to-year volume tracks usage, prescribing, and scrutiny, not a change in per-patient risk. Source: FDA FAERS.
Where magnesium oxide sits
magnesium oxide has more FDA adverse-event reports than 69% of the drugs FAERS tracks. A high position reflects how widely a drug is used and watched, not how dangerous it is.
Percentile across all drugs PlainMeds tracks by FAERS report volume. The dot is magnesium oxide; the line is the median (50th percentile).
FDA Adverse Event Report Analysis
Detailed analysis of 39,831 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2002–2025.
Total Reports
39,831
Reports Mentioning Death
6,280
15.8% of reports — not proof of cause
Hospitalization Reports
19,832
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | NAUSEA | 2,795 |
| 2 | DIARRHOEA | 2,580 |
| 3 | FATIGUE | 2,419 |
| 4 | DYSPNOEA | 2,054 |
| 5 | PNEUMONIA | 2,029 |
| 7 | PYREXIA | 1,829 |
| 8 | VOMITING | 1,666 |
| 9 | DEATH | 1,601 |
| 10 | HEADACHE | 1,598 |
| 11 | ANAEMIA | 1,465 |
| 12 | PAIN | 1,453 |
| 13 | DECREASED APPETITE | 1,440 |
| 14 | CONSTIPATION | 1,404 |
| 16 | FALL | 1,335 |
| 17 | ASTHENIA | 1,302 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Known Drug Interactions
Antacids and Sucralfate Clinical Impact: Concomitant administration of some antacids (magnesium oxide or aluminum hydroxide) and sucralfate can delay the absorption of naproxen. Intervention: Concomitant administration of antacids such as magnesium oxide or aluminum hydroxide, and sucralfate with naproxen tablets and naproxen sodium tablets is not recommended.
Mechanism: Magnesium oxide can slow down how quickly your body absorbs naproxen into your bloodstream. This might make the naproxen take longer to start working.
What to do: It is not recommended to take these two medications at the same time. Talk to your doctor or pharmacist about how to space out your doses.
This is a plain-language summary of interactions documented in FDA labeling, not individualized advice. Ask a pharmacist or prescriber before combining medications.
Common Questions
What is Mag-Ox used for?
How many tablets can I take each day?
Can I take Mag-Ox with food?
What should I do if I miss a dose?
How should I store Mag-Ox?
Can I take Mag-Ox if I am pregnant?
What if my symptoms do not improve?
Is Mag-Ox safe for children?
Can I take Mag-Ox with other medications?
What are the possible side effects of Mag-Ox?
What are the common side effects of magnesium oxide?
Does magnesium oxide interact with other medications?
What drug class is magnesium oxide?
Is magnesium oxide safe during pregnancy?
Related Medications in Mineral Supplement
Other drugs grouped near magnesium oxide - same-class peers and common alternatives.
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calcitriol
Rocaltrol
Calcitriol is a form of vitamin D that helps your body absorb and use calcium.
Compare with magnesium oxide →
calcium carbonate
Tums, Caltrate
Calcium carbonate is a medicine that can relieve heartburn and upset stomach.
Compare with magnesium oxide →
cholecalciferol
Vitamin D3
PNV-DHA is a multivitamin with minerals and essential fatty acids.
Compare with magnesium oxide →
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What the FDA Data Shows for magnesium oxide
The FDA label for magnesium oxide (sold under brand names such as Mag-Ox) classifies it as an over-the-counter product in the Mineral Supplement class. Mag-Ox treats acid indigestion and upset stomach. Official labeling lists 1 commonly reported side effect, including Diarrhea.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 39,831 voluntary reports. The database also lists 1 documented drug interaction derived from FDA labeling, with the top-flagged interaction rated moderate severity. NADAC pricing from CMS shows a generic unit cost of <$0.01.
Report counts do not establish causation, a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice, always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: October 21, 2025
Read our methodology - how this data is sourced, computed, and verified.
Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled and last refreshed May 2026. See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a correction.
All federal data sources used on this page
- FDA Orange Book - approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed - NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) - post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm - standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files - federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database - current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages