Magnesium Glycinate vs Citrate: Which Form Should You Take?

Magnesium citrate is the better-documented form and costs about half as much per milligram of magnesium. Glycinate is the pick if citrate loosens your stool or you want the glycine that comes bonded to it. No trial has compared the two for sleep, and the best-known sleep trial used neither. For most people, dose matters more than form.

The verdict

For most people: magnesium citrate, 200 to 400 mg of elemental magnesium a day. It has the most human absorption data of any form and costs about half as much per milligram as glycinate.

Glycinate wins when citrate loosens your stool, when you take the top of the range, or when you want the 1 to 2.5 grams of glycine that ride along with it.

The fact that decides it: in the one 60-day trial that compared forms head to head, citrate produced the highest serum magnesium. Every human absorption study of glycinate we could find is a single-dose study.

This page settles the form question only; for what magnesium does, how much you need, who runs short, and the interaction list, read the magnesium monograph.

Key Takeaways

• In the only 60-day trial comparing magnesium forms head to head (46 adults, 300 mg a day), citrate produced the highest serum magnesium and oxide did no better than placebo. Glycinate was not in it (Walker 2003, Magnesium Research).
• The human absorption data on glycinate come from three single-dose studies: 12 bowel-surgery patients in 1994 and two company-funded crossovers in 2018 and 2024. In neither did glycinate beat citrate.
• We could not find a published sleep trial that used magnesium glycinate. The best-known one used 500 mg a day of magnesium oxide; the only citrate sleep trial (100 adults, 320 mg a day, seven weeks) saw the placebo group improve as much.
• A 200 mg dose of magnesium bisglycinate carries about 1.2 grams of glycine. The glycine sleep studies used 3 grams, so one 200 mg serving delivers less than half the studied amount.
• Magnesium's laxative effect is osmotic: whatever the gut does not absorb pulls water into the colon. The trials that used magnesium for regularity gave about 900 mg a day as oxide, more than double the 350 mg supplemental Upper Limit (NIH ODS).

Side-by-side

Where they actually differ

A magnesium ion does not remember what it was bonded to. Once it crosses the gut wall there is no glycinate magnesium or citrate magnesium, only magnesium, doing the 300-enzyme job described in the monograph and our primer on magnesium supplements. The form matters in three places: how much of the tablet is magnesium, how the compound behaves in the gut, and what the other half of the molecule does once set free.

Density first. Elemental magnesium is the mineral itself, stripped of whatever it is bonded to, and the only number the trials dosed by. Bisglycinate is about 14 percent magnesium and anhydrous citrate about 16 percent, so 200 mg of magnesium means roughly 1.4 grams of glycinate or 1.2 grams of citrate. Neither fits in a small capsule, and the gap between them is trivial next to the gap between either and oxide, which is about 60 percent magnesium and barely absorbed (Firoz 2001).

Solubility is where they part ways. Citrate is 55 percent soluble in plain water and stays more soluble than oxide at every level of stomach acid (Lindberg 1990). Dissolving is good for absorption. It is also why the unabsorbed fraction loosens stool: a dissolved salt holds water in the bowel, and the laxative effect of every magnesium product is this osmotic pull plus some stimulation of gut motility (NIH ODS). Glycinate's other half is glycine, an amino acid the small intestine takes up on its own, so less is left behind to hold water. Unabsorbed magnesium still pulls water whatever it arrived with. Glycinate is gentler, not inert.

The absorption argument for glycinate is the dipeptide theory: magnesium diglycinate looks enough like a two-amino-acid peptide that part of a dose may be carried across the gut wall intact by a peptide transporter rather than the mineral channels (Schuette 1994). Plausible, and the basis of every "chelated magnesium absorbs better" label. The human evidence: 12 patients.

Then there is the glycine, the real reason glycinate gets recommended for sleep. Glycine is an amino acid that, in the brain, also works as an inhibitory neurotransmitter: it quiets signals. In healthy volunteers held to 75 percent of their usual sleep for three nights, 3 grams of glycine before bed cut next-day fatigue and improved psychomotor vigilance against placebo (Bannai 2012, Frontiers in Neurology). In rats, oral glycine brought on non-REM sleep sooner by widening skin blood vessels and dropping core temperature, acting on NMDA receptors in the suprachiasmatic nucleus, the body clock (Kawai 2015, Neuropsychopharmacology). Both studies came from Ajinomoto, which sells glycine. The arithmetic: 200 mg of magnesium as bisglycinate carries about 1.2 grams of glycine, 400 mg about 2.5 grams, and the studied dose was 3 grams.

What the trials say

Head to head first. Two human crossovers have put bisglycinate and citrate in the same study, and both were run by companies selling a third form. In 2024, 40 healthy adults took single doses of a microencapsulated magnesium, oxide, citrate, and bisglycinate on separate days. Citrate raised plasma magnesium at 4 hours and oxide at 1 hour. Bisglycinate did not move it. Single doses, plasma only, sponsor's product (Pajuelo 2024, Nutrients). In 2018, single 350 mg doses of a sucrosomial magnesium, citrate, oxide, and bisglycinate were compared; the sponsor's product won, and nothing in the report put bisglycinate ahead of citrate (Brilli 2018). In mice, citrate raised muscle and brain magnesium and glycinate did not stand out (Ates 2019). Grade for "glycinate absorbs better than citrate": Insufficient. For "citrate absorbs at least as well": Preliminary.

The citrate side's best trial is the one everyone cites, and for good reason. Forty-six healthy adults took 300 mg a day of elemental magnesium as amino acid chelate, citrate, or oxide, or placebo, double-blind, for 60 days. Citrate and the chelate beat oxide on 24-hour urinary magnesium; citrate alone produced the highest serum and salivary magnesium; oxide did not differ from placebo on anything. About 11 people per arm and surrogate markers are the limits (Walker 2003, Magnesium Research). Grade for citrate raising magnesium status: Moderate.

The glycinate side's best trial is older, smaller, and drawn from a surgical population. Twelve patients with part of the small intestine removed took a single 100 mg dose of isotope-labeled magnesium diglycinate or magnesium oxide in a double-blind crossover. For the group, absorption was the same, 23.5 versus 22.8 percent; in the four who absorbed oxide worst, the chelate doubled it, and every patient tolerated the chelate better. Surgical population, half a normal dose, no healthy controls (Schuette 1994, JPEN). Grade: Preliminary.

On sleep, the trials have never used glycinate. The strongest trial randomized 46 adults aged 60 to 75 with primary insomnia to 500 mg a day of elemental magnesium or placebo for eight weeks, given as two 414 mg magnesium oxide tablets. The magnesium group fell asleep faster, scored lower on the Insomnia Severity Index, and showed higher serum melatonin and lower cortisol; total sleep time did not change, and sleep was measured by questionnaire (Abbasi 2012). The one citrate trial gave 100 adults aged 51 to 85 with poor sleep 320 mg a day as citrate or a sodium citrate placebo for seven weeks. Sleep scores improved from 10.4 to 6.6 in both groups alike. The authors wrote that a placebo effect prevented them from telling whether magnesium did anything for sleep (Nielsen 2010, Magnesium Research). A 2021 meta-analysis pooled those two with a 12-person crossover on effervescent magnesium tablets (Held 2002) and found sleep onset 17 minutes faster, from evidence graded low to very low (Mah 2021). Oxide, citrate, effervescent. Not one glycinate arm. Grade for magnesium and sleep onset in older adults: Preliminary; for glycinate and sleep: Insufficient.

On regularity, the evidence is strong and belongs to oxide at doses no supplement label suggests. Ninety adults with chronic constipation took 1.5 grams a day of magnesium oxide, about 900 mg of elemental magnesium, or senna, or placebo for 28 days; 68 percent improved on magnesium against 12 percent on placebo (Morishita 2021, American Journal of Gastroenterology). Citrate does the same job at gram doses: citrate capsules plus bisacodyl cleaned the colon adequately in all 51 patients of a colonoscopy-prep trial (Eidensohn 2021). Across magnesium trials of every form, 11 to 37 percent of people reported gut side effects against 10 to 14 percent on placebo (Garrison 2020, Cochrane). Grade for magnesium loosening stool: Strong. For glycinate causing less of it than citrate: Preliminary, resting on mechanism and one tolerability finding.

What has not been tested is the comparison itself. No trial has randomized people to glycinate or citrate for weeks and measured sleep, stool, cramps, or magnesium status. No glycinate absorption study has run longer than one dose. The 1.2 to 2.5 grams of glycine inside a glycinate serving has never been tested as a sleep aid at that amount. Every "glycinate is better for sleep" claim is an inference stacked on an inference.

Who should pick which

If you want the form with the most human data

Citrate. It is the only one of the two with a 60-day randomized comparison behind it, and that trial put it first on serum and salivary magnesium (Walker 2003). Dose by the panel's elemental figure, 200 to 400 mg a day.

If citrate gives you loose stools, or your gut is easily upset

Glycinate, at the same elemental dose. Its glycine half is absorbed rather than left in the bowel, and it was better tolerated than oxide by every patient in the one direct comparison (Schuette 1994). Before switching, try citrate at 200 mg twice a day with meals; fractional absorption falls from about 65 percent at small doses to 11 percent at large ones (Fine 1991), so a split dose leaves less behind.

If sleep is the only reason you are buying magnesium

Neither form has a sleep trial behind it; the trial that showed a benefit used oxide at 500 mg in adults over 60, and the one citrate trial did no better than placebo. To test the glycine idea, take glycinate at 400 mg in the evening, which brings about 2.5 grams of glycine. If falling asleep is the specific problem, read the melatonin monograph first, and run through the sleep habits that have to be in place before any supplement. Our ranked guide to magnesium products for sleep prices six products on one day, and 5-HTP vs melatonin is the other evening comparison people run.

If price is the deciding factor

Citrate, in the larger bottle. At regular prices from the same brand, glycinate costs twice as much per milligram of magnesium and takes twice the tablets.

If you want a powder or an evening drink

Citrate. It dissolves in water (Lindberg 1990), which is why most magnesium drink powders are citrate, or carbonate that becomes citrate when it meets citric acid in the glass. Expect a sour taste.

Cost per effective day: which is cheaper?

Same brand on both sides, so the only variable is the form. Both NOW Foods tablets state the elemental figure on the panel and were priced on nowfoods.com on October 14, 2026.

The gap holds at the larger sizes: the 180-tablet glycinate was $23.99 on sale, or $0.53 a day at 400 mg; the 250-tablet citrate was $39.99, or $0.32. Glycinate runs 1.7 to 2 times the price for the same magnesium, and whether that premium is worth paying is a question about your gut, not about absorption.

We make neither of these. Our capsule, Good Magnesium, is a third option: 200 mg of elemental magnesium per capsule as an amino acid chelate (the panel reads rice protein chelate), a full 200 mg in one capsule where the glycinate above needs two tablets. It supports normal muscle relaxation and a calm nervous system without the digestive effect of a cheaper salt.* It is made in our own cGMP facility in Mt. Angel, Oregon; every batch is tested in our in-house lab for identity, potency, and purity; and certificates of analysis are published by lot on our lab-testing page. Sixty capsules are $21.99, which is $0.37 a day at 200 mg and $0.73 at 400 mg, checked 2026-10-14. What a chelate trades away is in our full review of the chelate form.

Next reads

• The full magnesium monograph: how much to take, every form compared, the interaction table, and who is likely to be short.
• Which magnesium products are worth buying for sleep, ranked: six products priced on the same day, two of them ours.
• Our full review of the chelate form: the third option, and what it gives up.