Magnesium glycinate vs. citrate: what actually differs

What each name describes

In a supplement, magnesium is supplied as part of a compound. Magnesium citrate is a magnesium salt of citric acid. Magnesium glycinate—also called magnesium bisglycinate or diglycinate—pairs magnesium with glycine.

The full compound weighs more than its magnesium portion. That is why a label can state a large compound amount while declaring a smaller amount of elemental magnesium. The Supplement Facts panel declares elemental magnesium per serving, which is the figure to use when comparing doses.

What absorption studies support

The clearest human evidence for magnesium citrate compares it with magnesium oxide. In a small study of healthy adults, Lindberg and colleagues found citrate was more soluble and produced a larger urinary-magnesium response than oxide. A later 60-day randomized trial by Walker and colleagues found that the organic forms studied—citrate and an amino-acid chelate—produced a greater long-term urinary-magnesium response than oxide; citrate also produced the highest reported serum response.

Evidence specific to glycinate is more limited. In a 12-person crossover study of patients with ileal resections, overall magnesium absorption did not differ significantly between diglycinate and oxide. Diglycinate performed better in a four-person subgroup with especially poor oxide absorption and was reported as better tolerated in that study population.

Small human studies have included citrate and bisglycinate in the same comparison, but they are short, formulation-specific, and not sufficient to establish a broadly applicable winner. Confidence that citrate is better absorbed than oxide is substantially stronger than confidence that either citrate or glycinate consistently outperforms the other.

The digestive difference needs context

Concentrated magnesium citrate solutions are used as saline laxatives. Their osmotic activity retains water in the gastrointestinal tract, which can produce a bowel movement. That establishes a real laxative use for magnesium citrate at medicinal doses; it does not predict exactly how every lower-dose citrate supplement will affect every person.

Glycinate is commonly selected by people seeking gastrointestinal tolerability, but strong head-to-head evidence confirming a consistent tolerance advantage over citrate remains limited. More broadly, high supplemental doses of magnesium can cause diarrhea, nausea, and abdominal cramping because unabsorbed magnesium salts have osmotic activity in the intestine and colon.

Compare the labels, not just the forms

Start with elemental magnesium per serving, the number of capsules or grams in that serving, and the number of servings in the container. One useful price comparison is cost per 100 mg of elemental magnesium. Serving burden, other ingredients, documentation, and personal tolerance can matter too.

Do not confuse compound weight with elemental magnesium. If marketing emphasizes a large citrate or glycinate amount, locate the elemental amount on the Supplement Facts panel before comparing products.

What the evidence does not settle

Available studies vary in dose, formulation, duration, population, and the measurements used as proxies for absorption. They do not establish that one of these two forms will produce a better health outcome for every user. A form name also cannot tell you whether a particular raw material is buffered or how a finished product was manufactured; those are documentation questions.

The tolerable upper intake level for magnesium from supplements and medications is 350 mg per day for adults. It is not a recommended intake and does not include magnesium naturally present in food. People with impaired kidney function have a higher risk of magnesium toxicity, and anyone considering a high dose or managing a medical condition should discuss it with a qualified healthcare professional.

Where our product fits

DECLARED Magnesium Glycinate provides 275 mg of elemental magnesium from 2,500 mg of magnesium glycinate per three-capsule serving. The bottle contains 90 capsules, or 30 labeled servings. We publish those figures so the product can be compared using the same standard described here—including against products in other forms.