magnesium oxide vs selenium
PlainMeds reviewed this comparison against our methodology in August 2026. It places FDA and CMS record fields side by side, without recommending either medication.
Side-by-side comparison of magnesium oxide and selenium. Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
Mag-Ox
Selenium
Magnesium oxide (Mag-Ox) is a mineral supplement. It helps relieve acid indigestion and upset stomach.
Selenium is a mineral supplement. It provides selenium, an essential nutrient, to your body.
Mag-Ox treats acid indigestion and upset stomach. It works by reducing the amount of acid in your stomach. Talk to your doctor if your symptoms do not improve.
This medicine is a mineral supplement. It helps increase the level of selenium in your body. Ask your doctor if this supplement is right for you.
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.
Selenium provides your body with selenium. Selenium is important for many bodily functions. It helps protect cells from damage and supports a healthy immune system.
- • Diarrhea
- • Tiredness
- • Headache
- • Diarrhea
- • Nausea
- • Pain
- Nausea 2,795
- Diarrhoea 2,580
- Fatigue 2,419
- Dyspnoea 2,054
- Pneumonia 2,029
- Fatigue 467
- Headache 326
- Diarrhoea 308
- Nausea 303
- Pain 280
No specific warnings noted.
No specific warnings noted.
Talk to your doctor before taking Mag-Ox if you are pregnant or breastfeeding. They can help you weigh the risks and benefits.
It is not known if selenium is safe to use during pregnancy or while breastfeeding. Talk to your doctor before using this supplement if you are pregnant or breastfeeding.
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How to Read This magnesium oxide vs selenium Comparison
magnesium oxide is classified in the Mineral Supplement drug class, while selenium sits within the Mineral Supplement class. Because both drugs share the same classification, they are often considered interchangeable in theory, but clinical outcomes rarely track that cleanly. Both drugs are available over the counter.
Adverse event totals above are pulled from the FDA's Adverse Event Reporting System (FAERS). For these top-ranked reactions alone, magnesium oxide has 11,877 submissions while selenium has 1,684. Those figures reflect cumulative reporting volume, not per-patient risk, so older, widely dispensed drugs typically look worse on count alone. No direct interaction between these two drugs is listed in our FDA-derived dataset, though co-prescription still warrants pharmacist review. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.
A table cannot represent individual circumstances. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This registry does not provide medical, treatment, substitution, or medication-change directions for magnesium oxide or selenium.
Registry boundary: This comparison displays source-record fields and does not provide individualized medical direction.