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MgO-400

21st Century
4.7
★ ★ ★ ★ ★
(1596 ratings)
Magnesium 483 mg
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Score90

A high-potency magnesium oxide tablet with added calcium for bone and heart health support.

How scoring works
Quantity:90 Tablet(s) • (45 servings)
Goals:
Energy
Digestive Health
Testosterone Support

Score 90

A high-potency magnesium oxide tablet with added calcium for bone and heart health support.

How scoring works
$5.88($0.13 per serving)
Pure Formulas
$ 7.94
Amazon
$ 5.24
Walmart
$ 10.99
iHerb
$ 5.24
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Analysis

This supplement provides 483 mg of elemental magnesium as an oxide and 130 mg of calcium. This combination is aimed at supporting bone density and basic cardiovascular function through essential mineral repletion.

While the oxide form isn't the most bioavailable for the nervous system, it is very high in elemental weight. It is a good choice for people who want an economical, one-tablet-a-day way to ensure they are meeting their basic mineral requirements.

Pros

  • High elemental magnesium yield
  • Added calcium for bone support
  • Very affordable price
  • Once-daily tablet is convenient

Cons

  • Inorganic forms have lower absorption
  • Tablet can be quite hard and large
  • Risk of digestive discomfort

Warnings

  • Take with a full meal
  • Check with a professional if you have kidney issues

Nutrient quality

75 High impact

The combination of structural minerals provides foundational skeletal support but utilizes poorly bioavailable inorganic forms. While elemental yields are high, the risk of digestive irritation is increased.

Ingredient transparency

97 Highest impact

Labeling clearly identifies the mineral forms used and specifies the total elemental amount provided per tablet. Disclosure is comprehensive and allows consumers to accurately evaluate the supplement's total load.

Customer satisfaction

94 Highest impact

Strong ratings over a large number of reviews demonstrate consistent consumer satisfaction and reliable results. Feedback confirms the product's effectiveness for leg cramps and structural support.

Value for money

94 Highest impact

Extremely low cost per serving makes this an attractive option for basic structural mineral support. While the mineral forms are budget-tier, the affordability offers significant value for long-term use.

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Goals

Impact
High effect
A- Goal FitB- Strength of SupportC- CoverageA Formula Quality

Magnesium oxide provides a foundational source of the essential mineral required for ATP-dependent enzymatic reactions. Magnesium serves as a critical cofactor for mitochondrial energy production, making it a foundation for cellular stamina.

A 483mg dose of elemental magnesium is high and appears well aligned with addressing mineral-related tiredness. However, the use of magnesium oxide as the primary source limits the overall absorption potential compared to organic chelates.

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Impact
High effect
B+ Goal FitC+ Strength of SupportD+ CoverageA+ Formula Quality

Magnesium oxide provides a powerful osmotic mechanism that can help support bowel regularity and motility. This inorganic mineral is effective for drawing water into the colon to assist in stool softening.

The 483mg elemental dose is substantial and well-aligned with goals for occasional constipation relief. High brand visibility and an economical price point make this a frequent choice for simple digestive support.

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Impact
High effect
B+ Goal FitC Strength of SupportD+ CoverageA- Formula Quality

Magnesium Oxide is provided at a 483 milligram dose to support general wellness and mineral status. Magnesium is important for maintaining healthy bioavailable hormone levels by reducing globulin binding.

While the dose is potent, the oxide form is known for very low systemic absorption compared to organic salts. This formula is a cost-effective choice but lacks the biological activity of more premium mineral supplements.

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Impact
Moderate effect
C- Goal FitC Strength of SupportD CoverageA- Formula Quality

Magnesium oxide is provide at an elemental dose of 483 mg per tablet to support foundational mineral levels and help regulate nervous system excitability. Magnesium is a critical nutrient during periods of high stress when biological stores may be rapidly depleted.

While the elemental weight is substantial, the inorganic oxide form has low systemic bioavailability compared to chelated alternatives. It provides basic mineral support but may be less effective for systemic stress modulation than other magnesium salts.

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Impact
Moderate effect
A Goal FitD- Strength of SupportD- CoverageC- Formula Quality

Magnesium Oxide provides an elemental source of a mineral required for hundreds of metabolic reactions. Calcium Carbonate is included to support structural bone health.

The use of poorly absorbed mineral forms and an excessively high dose may lead to digestive discomfort. It provides a basic mineral supply but lacks the bioavailability of chelated alternatives.

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Impact
Moderate effect
C+ Goal FitC- Strength of SupportF CoverageC+ Formula Quality

Supplies 483 mg of elemental magnesium in the oxide form to support heart muscle function and vascular healthy. Magnesium is a vital mineral for maintaining cardiovascular rhythms and supporting blood pressure regulation.

Magnesium Oxide is widely recognized for having very low systemic absorption, meaning much of the mineral may not reach the cardiovascular system. While the dose is high, the poor bioavailability of the oxide form limits its functional effectiveness for heart-specific goals.

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Ingredients

IngredientAmount per serving
Calcium (Calcium Carbonate)
130 mg
elemental Magnesium (Magnesium Oxide)
483 mg
Gluten Free Adults 18–50
Report overview
F Active Ingredient Quality & BioavailabilityC+ Dose, Safety & Label TransparencyD+ Value
MgO-400 is a straightforward, budget-conscious magnesium oxide supplement. It provides a standard dose of the mineral but suffers from the poor bioavailability common to inorganic oxide forms.
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