How Is Magnesium Absorbed in the Body?

Magnesium absorption is not random.

It is a regulated, dose-dependent process that occurs primarily in the small intestine.

Understanding how magnesium is absorbed helps explain:

• Why form matters

• Why dose matters

• Why splitting doses can improve tolerance

• Why some supplements are better absorbed than others

Let’s walk through the biology.

In Brief

• Magnesium is absorbed mainly in the small intestine
• Absorption occurs via passive diffusion and active transport
• Absorption efficiency decreases at higher doses
• Vitamin D status influences magnesium handling
• Form affects solubility and tolerance

Where Is Magnesium Absorbed?

Magnesium is absorbed primarily in:

• The distal small intestine (ileum)

• The colon (to a lesser extent)

Only about 30–50% of dietary magnesium is typically absorbed under normal conditions.

Absorption increases when intake is low.
Absorption decreases when intake is high.

The body adjusts.

Two Main Absorption Pathways

Magnesium absorption occurs via two mechanisms:

1️⃣ Passive Paracellular Diffusion

This accounts for the majority of magnesium absorption.

It occurs:

• Between intestinal cells

• Driven by concentration gradients

• More active at higher intakes

When you consume larger doses, more magnesium moves through this pathway.

However, efficiency (percentage absorbed) decreases as dose increases.

2️⃣ Active Transcellular Transport

This occurs through specialised channels:

• TRPM6

• TRPM7

These transporters regulate magnesium uptake when intake is lower.

They are saturable — meaning they can only transport so much at a time.

This is why megadosing does not proportionally increase absorption.

How Much Magnesium Is Actually Absorbed?

Absorption depends on:

• Dose
• Form
• Gut health
• Vitamin D status
• Overall magnesium status

Typical fractional absorption:

• Lower doses → higher percentage absorbed

• Higher doses → lower percentage absorbed

Example:

200 mg may absorb proportionally better than 600 mg taken at once.

This is why split dosing can improve proportional uptake.

See:
→ How Much Magnesium Do You Actually Need?

Does Magnesium Form Affect Absorption?

Yes — largely due to solubility and tolerance.

Magnesium must dissolve before it can be absorbed.

Highly soluble forms generally absorb better.

Common Forms Compared

Magnesium oxide contains more elemental magnesium per gram — but lower solubility may limit proportional absorption.

Ranade & Somberg, 2001
Reviewed differences in magnesium salt bioavailability.

See:
→ Chelated vs Non-Chelated Magnesium
→ Why Most Magnesium Supplements Use Oxide

What Reduces Magnesium Absorption?

Magnesium absorption may be reduced by:

• Very high doses taken at once
• Gastrointestinal disorders
• Chronic diarrhoea
• Competing high-dose minerals (iron, calcium)
• Alcohol excess

See:
→ Does Magnesium Compete with Other Minerals?

What Improves Magnesium Absorption?

Magnesium absorption may improve when:

• Taken in moderate doses
• Split across the day
• Taken with food (for tolerance)
• Vitamin D status is adequate

Magnesium and vitamin D work synergistically in the body.

Low magnesium may impair vitamin D activation.

What Happens After Absorption?

Once absorbed:

• Magnesium enters the bloodstream

• It is distributed to soft tissues

• ~50–60% is stored in bone

• The kidneys regulate excretion

Serum magnesium represents only ~1% of total body magnesium.

This is why blood levels may not reflect total body stores.

See:
→ Are Most People Magnesium Deficient?

Does More Magnesium Mean More Benefit?

No.

Magnesium absorption is saturable.

Large single doses:

• Increase gastrointestinal side effects

• Decrease proportional absorption

Consistent moderate intake is more effective than occasional megadoses.

Where Magnesium Complex Fits

Arbor Vitamins Magnesium Complex provides:

• 264 mg elemental magnesium

• From glycinate and taurate

These forms are selected for:

• Solubility

• Tolerance

• Suitability for daily use

Explore here:
👉 https://arborvitamins.com/products/arbor-vitamins-magnesium-complex-bisglycinate-taurate

FAQ

Where is magnesium absorbed?

Primarily in the small intestine (ileum), with minor absorption in the colon.

How much magnesium does the body absorb?

Typically 30–50% of intake, depending on dose and status.

Is magnesium oxide absorbed?

Yes, but fractional absorption may be lower compared to more soluble forms.

Does splitting magnesium improve absorption?

Splitting doses may improve proportional absorption and reduce side effects.

Final Thoughts

Magnesium absorption is:

Regulated
Dose-dependent
Form-dependent

It is not about the highest label number.

It is about what your body can dissolve, transport and retain.

Consistency and form matter more than headline dosage.