Magnesium glycinate and magnesium citrate compared

The short answer

No trial has shown that one of these forms is clearly better than the other at raising magnesium levels over weeks of use. What separates them is more practical: how much magnesium each delivers per gram, how each tends to affect the gut, how much research exists on each, and what else arrives with the magnesium.

This guide goes through each of those, and is clear about where the evidence is thin.

What each form is

Magnesium citrate is magnesium paired with citric acid, the same acid found in citrus fruit. It dissolves readily, even in plain water, which is one reason it is widely used.

Magnesium glycinate is a magnesium ion held by two molecules of the amino acid glycine. It is also sold as magnesium bisglycinate, and some labels call it magnesium amino acid chelate. Our guide to what magnesium glycinate is covers it in detail.

Both are organic forms of magnesium, which is the usual shorthand for magnesium bound to a carbon-based molecule. Magnesium oxide, by contrast, is an inorganic form.

How much magnesium each one delivers

	Magnesium citrate	Magnesium glycinate
Magnesium by weight	About 16% (anhydrous), lower in hydrated grades	About 14%
Compound needed for 300 mg of magnesium	About 1,850 mg (anhydrous)	About 2,130 mg
What comes with the magnesium	Citrate	Glycine, around 1.5 g per 250 mg of magnesium

The difference in magnesium content is smaller than it looks on paper, because commercial magnesium citrate often carries water in its structure, which lowers its magnesium share. Both forms are bulky compared with magnesium oxide, which is why products based on either tend to need larger or more numerous capsules.

Whichever form you are looking at, compare the "equivalent to magnesium" figure on the label rather than the compound weight. Our guide to elemental magnesium explains why.

What the absorption research shows

Magnesium absorption is hard to measure, and the studies comparing forms are few and small. With that in mind, here is what exists.

Magnesium citrate against magnesium oxide. A 1990 study found magnesium citrate was far more soluble than magnesium oxide in conditions mimicking the stomach, and produced a larger rise in urinary magnesium after a single dose in healthy volunteers. A 2003 randomised, double-blind trial in 46 healthy adults compared magnesium citrate, a magnesium amino acid chelate and magnesium oxide at 300 mg of magnesium a day for 60 days. Both organic forms showed greater absorption than the oxide by 60 days, and the citrate group had the highest average blood magnesium, both after the first dose and at the end. The chelate in that trial was not specified as glycinate, so it cannot be read directly as a result for magnesium glycinate.

Magnesium glycinate against magnesium oxide. A 1994 stable-isotope trial in 12 patients who had undergone bowel surgery found similar total absorption from the two forms, about 23% each. Magnesium from the glycinate peaked earlier and followed a different absorption curve, which the researchers attributed to part of it being absorbed intact through a separate pathway.

The two compared directly. The only study we found that tested both forms side by side was a 2024 randomised crossover study in 40 healthy adults. Each person took a single 375 mg dose of magnesium as oxide, citrate, bisglycinate and a microencapsulated magnesium oxide ingredient, a week apart, and plasma magnesium was measured over six hours. Magnesium citrate produced a significant rise in plasma magnesium at four hours. Magnesium bisglycinate did not produce a significant rise at any time point.

That result needs to be read carefully. When the researchers compared the forms against each other, they found no significant differences between any of them in the total rise over six hours, or in the size of the increase at one or four hours. The study measured a single dose over one day, not regular use. The doses were taken as powders rather than capsules. And the study was designed to evaluate the microencapsulated ingredient, with authors from the company that makes it.

The broader picture. A 2021 systematic review of magnesium supplement studies concluded that all magnesium supplements can maintain normal levels in healthy people who are not already low. The same could not be assumed for older people, people who are unwell, or people with low levels to begin with.

Taken together, magnesium citrate has somewhat more absorption data in healthy adults, and fares consistently well in it. The research on magnesium glycinate absorption is thinner and more mixed. No study has shown that either delivers meaningfully more magnesium to the body over weeks of regular use. Our explainer on magnesium absorption and bioavailability covers why these studies disagree so often.

How each one affects the gut

This is where the two forms tend to differ most in everyday use.

Magnesium citrate is used in larger doses as an osmotic laxative, including as a bowel preparation before colonoscopy. It draws water into the bowel. For some people that effect is a reason to choose it. For people taking magnesium every day for other reasons, it can be a reason to watch the dose.

Magnesium glycinate has a good tolerability record in trials. In the 1994 trial it was better tolerated than magnesium oxide by every patient. In a 2025 trial of 155 adults taking 250 mg of magnesium a day as bisglycinate or placebo for four weeks, side effects were reported less often in the magnesium group than the placebo group.

Neither form is free of gut effects, though. In the 2024 single-dose study, participants reported more bowel movements with magnesium citrate than with the microencapsulated ingredient, and more stomach heaviness with magnesium bisglycinate. One participant left that study because of side effects after taking the bisglycinate. Individual responses vary, and gut effects become more likely as the dose rises with either form. Our guide to side effects and interactions covers this in more detail.

What has been studied for each form

Much of the magnesium research either uses other forms or does not say which form was used, so findings about magnesium in general cannot be credited to either of these two.

For magnesium glycinate specifically, there are three human studies of note: the 1994 absorption trial, a placebo-controlled trial for leg cramps in pregnancy, and the 2025 placebo-controlled trial in adults reporting poor sleep. We review that sleep trial in magnesium glycinate and sleep.

For magnesium citrate, the studies we have described here are mostly about absorption rather than about specific outcomes.

No trial has compared the two forms head to head for any health outcome, including sleep.

Interactions with medicines

Both forms interact with the same medicines as other magnesium supplements, including oral bisphosphonates, some antibiotics, diuretics and long-term proton pump inhibitors.

One recent study looked at form specifically. In a 2025 crossover trial in 15 healthy adults, taking levothyroxine, a thyroid hormone medicine, together with magnesium reduced how much levothyroxine was absorbed. The reduction was 12% with magnesium aspartate, which was statistically significant, and 7% with magnesium citrate, which was not. Magnesium glycinate was not tested. The researchers advised that people taking levothyroxine should take it separately from magnesium.

If you take any regular medicine, ask your pharmacist how to time a magnesium supplement around it, whichever form you are considering.

Weighing them up

If you are comparing products, these are the questions the evidence can actually help with:

• How much magnesium is in the dose? Compare the equivalent figures, not the compound weights.
• How does your gut respond? Magnesium citrate is more likely to have a laxative effect as the dose rises. Magnesium glycinate has generally been well tolerated, though not by everyone.
• Does the total add up? The 350 mg upper level for supplemental magnesium applies whichever form you take, and includes magnesium from antacids, laxatives and multivitamins.
• Are you on other medicines? Timing matters more than form.

A pharmacist can help you compare specific products. If you are concerned about your magnesium levels, speak with your doctor. Nothing on this page is a substitute for individual medical advice.