Magnesium citrate is about 16% magnesium by formula weight and magnesium bisglycinate about 14%, so citrate reaches the same elemental dose with roughly an eighth less powder. Both are soluble. At larger doses citrate pulls water into the gut, which is why it is also used as a laxative; glycinate is usually chosen for tolerability, on evidence that is thinner than its reputation.
Two percentage points of magnesium is the least interesting difference between these two bottles. What follows is the arithmetic, the four small human studies that put either salt against anything, and the gap where a head-to-head trial of the two should be.
What is the difference between magnesium glycinate and magnesium citrate?
They are two salts of the same mineral. Citrate binds magnesium to citric acid; glycinate, written bisglycinate on the more precise labels, holds one magnesium between two molecules of the amino acid glycine. By formula weight citrate is about 16% magnesium and bisglycinate about 14%. The magnesium is identical. What differs is the carrier, how much compound a dose needs, and what any unabsorbed share does in the gut.
That last difference is the one with consequences. Magnesium that is not absorbed stays in the bowel and holds water there. Every salt leaves some behind at a large enough dose — oxide most reliably, because so little of it is absorbed — and citrate leaves enough behind at laxative doses to be used for that job. Of these two forms, citrate is the one studied at both ends: how well it is absorbed, and what it does to the bowel. Glycinate has been studied far less at either.
Does magnesium citrate have more magnesium than glycinate?
Slightly, by weight. Citrate is about 16% magnesium and bisglycinate about 14%, so a gram of citrate carries about 160 mg of magnesium and a gram of bisglycinate about 140 mg. Those are formula-weight ceilings for the pure, dry compounds — arithmetic, not laboratory figures. A hydrated citrate carries less, about 12% as the nonahydrate. The only number that settles a particular bottle is the elemental figure in its Supplement Facts panel.
Run forward to a real dose, the gap is about a quarter of a gram of powder. The reference amount below is 275 mg of magnesium because that is the elemental figure printed on Night Work's label, and it is a label figure: nothing in this table was measured.
| Form | Magnesium by weight | Compound needed for 275 mg of magnesium |
|---|---|---|
| Magnesium citrate | about 16% | about 1,700 mg |
| Magnesium citrate, nonahydrate | about 12% | about 2,310 mg |
| Magnesium bisglycinate | about 14% | about 1,950 mg |
| Night Work, by its label | 11% (275 ÷ 2,500) | 2,500 mg of magnesium glycinate |
The first three rows are 275 divided by the unrounded magnesium fraction behind each percentage, rounded to the nearest 10 mg; the formula weights are PubChem's, the values the rest of this Journal uses. The last row is our own panel run through the same division. It lands under the 14% a pure, dry bisglycinate would show, which is the normal direction: a raw material is rarely pure and rarely dry, and bound water adds weight without adding magnesium. A panel that divides out above its form's ceiling is the one worth questioning. The method, with the atomic masses printed so it can be checked, is in how to read an elemental magnesium label, and the same division across every common form sits in supplement forms compared.
Is magnesium citrate absorbed better than glycinate?
Possibly, but the comparison has barely been run. The NIH Office of Dietary Supplements lists citrate among the forms small studies found better absorbed than oxide and sulfate; glycinate is not on that list. In a 2024 crossover that gave 375 mg of magnesium as each form, plasma magnesium rose at four hours after citrate and did not rise significantly after bisglycinate. That trial had 40 participants, one dose of each form, and a sponsor selling a competing ingredient.
The Office's reasoning is about solubility, not chelation: "Forms of magnesium that dissolve well in liquid are more completely absorbed in the gut than less soluble forms." Citrate's place on its list traces partly to Lindberg and colleagues (Journal of the American College of Nutrition, 1990), who found magnesium citrate 55% soluble even in plain water, where magnesium oxide barely dissolved at all, and saw urinary magnesium rise far more after a 25 mmol load of citrate, roughly 600 mg of magnesium, than after the same load of oxide. That is citrate against oxide. It says nothing about glycinate either way.
The trial that put the two forms side by side is Pajuelo and colleagues (Nutrients, 2024): randomised, double-blind, crossover, 40 healthy adults aged 20 to 55, a seven-day low-magnesium diet before each product, blood drawn at one, four and six hours. Citrate raised plasma magnesium by about 7.5% at four hours. Bisglycinate produced no significant rise at any time point. Three limits travel with that finding. The trial was funded by the maker of the microencapsulated product it set against the other three. A six-hour plasma curve after one dose is not magnesium status — the Office of Dietary Supplements notes that less than 1% of the body's magnesium is in serum, held under tight control. And 375 mg is above the 350 mg upper level for supplemental magnesium, so it is not a daily dose to copy. We sell glycinate and print the trial anyway; the long version is in magnesium glycinate side effects.
The longest comparison is older and smaller. Walker and colleagues (Magnesium Research, 2003) gave 46 healthy adults 300 mg of magnesium a day for 60 days as an amino-acid chelate, as citrate, as oxide, or as placebo. Citrate produced the highest mean serum magnesium of the four arms after the first dose and again after 60 days; oxide did not differ from placebo. Forty-six people across four arms is about 11 or 12 per arm, and the abstract does not say which amino acid the chelate used, so it cannot be read as a glycinate finding.
Is magnesium citrate a laxative?
At larger doses, yes. PubChem's chemical record for magnesium citrate lists a role as a laxative, and the NIH Office of Dietary Supplements, which notes that magnesium is a primary ingredient in some laxatives, puts the laxative effect of magnesium salts down to osmosis: salt that is not absorbed stays in the intestine and colon and holds water there. At supplement doses the same pull is weaker, but it does not switch off.
The Office describes the high-dose picture plainly: large amounts of magnesium from supplements or medicines often produce loose stools, sometimes with nausea and abdominal cramping. At 375 mg in the 2024 crossover, more participants reported increased bowel movements after citrate, and after oxide, than after the sponsor's product, on a self-reported questionnaire. That is the citrate trade in one line: a form that dissolves well is absorbed well, and whatever share is not absorbed still acts on the bowel.
It is also why the ceiling on supplemental magnesium exists in the form it does. The Institute of Medicine's 1997 limit, in its own words, "represents intake from pharmacological agents only and does not include intake from food and water." Supplements and medicines count against 350 mg a day; spinach does not. What that line means for a cabinet with more than one magnesium product in it is set out in can you take too much magnesium.
Is magnesium glycinate gentler on the stomach than citrate?
That is its reputation, and the direct evidence is thin. We found no randomised trial that compared the two forms' gut effects with each other at the same elemental dose. The closest is the 2024 crossover: at 375 mg, more participants reported increased bowel movements after citrate and more reported stomach heaviness after bisglycinate, each counted only against the sponsor's product, never against each other. Glycinate's gentleness is a reasonable expectation, not a measured advantage over citrate.
The expectation has two legs. The first is that citrate is the salt used as a laxative and glycinate is not. The second is a mechanism: some magnesium diglycinate may be absorbed intact through the gut's dipeptide transporters, which would leave less salt behind to hold water. That idea comes from Schuette and colleagues (JPEN, 1994), and the trial behind it is small and specific: 12 patients with ileal resection, a 100 mg labelled dose of chelate or oxide, absorption tied overall at 23.5% against 22.8%, and the chelate ahead only in the four patients with the most impaired absorption, 23.5% against 11.8%. That trial compared glycinate with oxide, not citrate, and the 2024 plasma finding sits awkwardly with the idea that glycinate leaves less behind.
So the honest version is narrower than the aisle. Glycinate is the form people choose when a looser bowel is the effect they want least, and nothing in the evidence argues against that choice. Nothing in it measures the margin either.
Which is better for daily use, magnesium citrate or glycinate?
For a dose taken every day, the better form is the one your gut tolerates at the elemental dose you need, counted against the 350 mg daily ceiling on supplemental magnesium. Citrate has the stronger absorption record in small human studies and the stronger laxative effect at higher doses. Glycinate is chosen for tolerability, on thinner evidence. Either form is only as good as its elemental figure, so read that number rather than the compound weight on the front.
Three checks settle it on any bottle, ours included:
- Find the elemental figure in the panel. If only a compound weight is printed, the dose cannot be known from the label.
- Divide it by the compound weight. Up to about 16% is consistent with citrate and up to about 14% with bisglycinate; a figure above its form's ceiling points to a blend or a different salt. The words on a panel are decoded in the supplement label glossary.
- Add every supplemental source in the day — multivitamin, electrolyte powder, antacid — and keep the total at or under 350 mg. How much that leaves food to supply is worked through in how much magnesium per day.
The same comparison against the other common forms runs in glycinate against oxide, glycinate against malate and chloride against glycinate, and the buying procedure end to end is in how to choose a magnesium supplement.
What the research does not show
No trial has compared magnesium glycinate with magnesium citrate over weeks on any measure of magnesium status. The one direct comparison is a single dose per form, six hours of plasma, 40 people and an interested sponsor. The longer trial that favoured citrate used an unnamed amino-acid chelate in arms of about a dozen people. Neither supports a percentage advantage for either form, and this page quotes none.
The salt on a label also predicts less than it seems to. In an industry-funded laboratory comparison of 15 commercial products, Blancquaert and colleagues (Nutrients, 2019) found two citrate products that released essentially all of their magnesium within two hours and a third that released 64% in acid and 35% in a pH 6.8 buffer. Same salt, different tablets. That was a dissolution model, not a person, and none of the citrate or glycinate products went on to a human test.
Nor do these studies show either form doing anything a man who trains would notice. They measured magnesium in blood and urine, not performance and not how anyone felt. What magnesium does in the body belongs to the mineral, whichever salt carries it. Magnesium supports normal muscle function.* The complete evidence table, form by form, is in the magnesium research summary.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Where Night Work sits
Night Work is magnesium glycinate in capsules: by its label, 275 mg of elemental magnesium from 2,500 mg of magnesium glycinate per three-capsule serving, 30 servings. It is the only supplemental magnesium in the TARE range, so the label's 275 mg is the whole of the range's supplemental total, 75 mg under the 350 mg tolerable upper intake level. We chose glycinate for the reason this page gives and with the limits this page prints. What is and is not measured for Night Work is set out on Testing & Certification.
Sources
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals (updated 6 January 2026). NIH Office of Dietary Supplements
- PubChem. Trimagnesium dicitrate (magnesium citrate), CID 6099959 (molecular formula C12H10Mg3O14). pubchem.ncbi.nlm.nih.gov
- PubChem. Magnesium citrate nonahydrate, CID 53249332 (molecular formula C12H28Mg3O23). pubchem.ncbi.nlm.nih.gov
- Pajuelo D, Meissner JM, Negra T, et al. Nutrients 2024;16(24):4367. PubMed 39770988
- Walker AF, Marakis G, Christie S, Byng M. Magnes Res 2003;16(3):183-191. PubMed 14596323
- Lindberg JS, Zobitz MM, Poindexter JR, Pak CY. J Am Coll Nutr 1990;9(1):48-55. PubMed 2407766
- Schuette SA, Lashner BA, Janghorbani M. JPEN J Parenter Enteral Nutr 1994;18(5):430-435. PubMed 7815675
- Blancquaert L, Vervaet C, Derave W. Nutrients 2019;11(7):1663. PubMed 31330811
- Institute of Medicine. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. National Academy Press, 1997. nationalacademies.org