Magnesium Bioavailability | Glycinate vs Citrate vs Oxide

One tablet, three chemical forms, three very different fates.

Magnesium is bound to a partner molecule. The partner decides how well it dissolves and absorbs.

A high-elemental oxide tablet can absorb worse than a small glycinate dose. Bioavailability beats raw milligrams.

Stomach acid and small intestine fluid break the salt apart.

Glycinate binds magnesium to glycine, an amino acid. This chelate stays soluble through the gut.

Oxide is an inorganic salt with low solubility. Much of it stays undissolved in the lumen.

Only dissolved, free Mg²⁺ ions can cross into the bloodstream.

Active transport favors chelated glycinate. Passive paracellular flow favors citrate somewhat.

Undissolved oxide draws water osmotically into the gut. This produces its strong laxative pull.

Absorbed ions raise serum magnesium at different rates.

Only the fraction that crosses the gut wall counts. Label milligrams overstate oxide's real delivery.

Glycinate produces a smoother rise, less GI upset. Oxide's rise is small and often diarrhea-limited.

The best form depends on what you are trying to fix.

Glycinate crosses well and avoids gut irritation. Glycine itself has a mild calming effect.

Oxide's poor absorption is the whole point here. Unabsorbed salt draws water, easing constipation.

Citrate balances decent absorption and affordability. It is a common first-line supplement choice.

Product	Indication	Trial Design	Key Result
Magnesium Glycinate	Sleep, anxiety, muscle relaxation	Amino-acid chelate, active transport uptake	~80% absorption, minimal laxative effect
Magnesium Citrate	General deficiency correction	Organic acid salt, mixed absorption routes	~35% absorption, moderate cost and GI effect
Magnesium Oxide	Constipation, occasional laxative use	Poorly soluble salt, osmotic water draw	~4% absorption but strong laxative action