Equal elemental amount · snapshot 2026-08-10

Magnesium carbonate vs Magnesium oxide

For 200 mg elemental magnesium, magnesium carbonate requires 694–807 mg of compound and magnesium oxide requires 332 mg, using the chemistry accompanying the 2026-08-10 label snapshot. This difference follows from the magnesium fraction of each compound. It requires no absorption-study assumption: the same elemental mass travels with a different mass of the rest of the compound.

Show the working

Same elemental amount, different compound mass

At 100, 200 and 400 mg elemental magnesium, the chemistry accompanying the 2026-08-10 snapshot uses 24.78–28.83% magnesium by mass for magnesium carbonate and 60.32% for magnesium oxide; dividing the elemental amount by these fractions gives the compound masses below.

Formula, magnesium fraction and compound mass · snapshot context 2026-08-10
Property	Magnesium carbonate	Magnesium oxide
Elemental Mg by compound mass	24.78–28.83%	60.32%
Anhydrous reference formula	MgCO₃	MgO
Molar mass of that reference formula	84.31 g/mol	40.30 g/mol
Composition interval	anhydrous or hydrated; labels rarely state which	One formula fraction used for MgO in this model.
Compound for 100 mg elemental Mg	347–404 mg	166 mg
Compound for 200 mg elemental Mg	694–807 mg	332 mg
Compound for 400 mg elemental Mg	1,387–1,614 mg	663 mg
Size 00 capsules for 100 mg elemental Mg	1 capsules at 730 mg compound fill each	1 capsules at 730 mg compound fill each
Size 00 capsules for 200 mg elemental Mg	1–2 capsules at 730 mg compound fill each	1 capsules at 730 mg compound fill each
Size 00 capsules for 400 mg elemental Mg	2–3 capsules at 730 mg compound fill each	1 capsules at 730 mg compound fill each

Molar masses refer to the displayed anhydrous formulas. Hydrated or composition-ambiguous readings use the full fraction interval from the chemistry layer. Compound masses are rounded to whole milligrams; capsule counts round the unrounded mass divided by 730 mg upward at each interval endpoint.

Magnesium carbonate: 200 mg worked example

For 200 mg elemental magnesium as magnesium carbonate, the chemistry accompanying the 2026-08-10 snapshot requires 694–807 mg of compound: 200 ÷ 0.2883 through 200 ÷ 0.2478, rounded to whole milligrams.

That requires 1–2 size 00 capsules at 730 mg of compound per capsule, before other ingredients. The mass interval reflects anhydrous or hydrated; labels rarely state which.

Magnesium oxide: 200 mg worked example

For 200 mg elemental magnesium as magnesium oxide, the chemistry accompanying the 2026-08-10 snapshot requires 332 mg of compound: 200 ÷ 0.6032, rounded to whole milligrams.

That requires 1 size 00 capsules at 730 mg of compound per capsule, before other ingredients. The model uses the MgO fraction throughout.

Compound mass reference in 25 mg elemental increments

40 arithmetic inputs from 25 to 1,000 mg elemental magnesium are converted below using the two salt fractions and the capsule capacities accompanying the 2026-08-10 snapshot, calculated 2026-09-13. These are mass-conversion inputs, independent of any consumption schedule.

Each compound interval divides the elemental input by the high and low magnesium fractions. Each capsule interval divides those unrounded compound masses by the listed fill capacity, then rounds upward. The three capsule sizes use 545, 730 and 1100 mg of compound per capsule respectively, before other ingredients.

Magnesium carbonate and Magnesium oxide · 40 elemental inputs · 2026-09-13
Elemental Mg	Magnesium carbonate: compound mass	Magnesium carbonate: size 0	Magnesium carbonate: size 00	Magnesium carbonate: size 000	Magnesium oxide: compound mass	Magnesium oxide: size 0	Magnesium oxide: size 00	Magnesium oxide: size 000
25 mg elemental Mg	87–101 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill	41 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
50 mg elemental Mg	173–202 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill	83 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
75 mg elemental Mg	260–303 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill	124 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
100 mg elemental Mg	347–404 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill	166 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
125 mg elemental Mg	434–504 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill	207 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
150 mg elemental Mg	520–605 mg compound	1–2 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill	249 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
175 mg elemental Mg	607–706 mg compound	2 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill	290 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
200 mg elemental Mg	694–807 mg compound	2 capsules at 545 mg fill	1–2 capsules at 730 mg fill	1 capsules at 1100 mg fill	332 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
225 mg elemental Mg	780–908 mg compound	2 capsules at 545 mg fill	2 capsules at 730 mg fill	1 capsules at 1100 mg fill	373 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
250 mg elemental Mg	867–1,009 mg compound	2 capsules at 545 mg fill	2 capsules at 730 mg fill	1 capsules at 1100 mg fill	414 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
275 mg elemental Mg	954–1,110 mg compound	2–3 capsules at 545 mg fill	2 capsules at 730 mg fill	1–2 capsules at 1100 mg fill	456 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
300 mg elemental Mg	1,041–1,211 mg compound	2–3 capsules at 545 mg fill	2 capsules at 730 mg fill	1–2 capsules at 1100 mg fill	497 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
325 mg elemental Mg	1,127–1,312 mg compound	3 capsules at 545 mg fill	2 capsules at 730 mg fill	2 capsules at 1100 mg fill	539 mg compound	1 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
350 mg elemental Mg	1,214–1,412 mg compound	3 capsules at 545 mg fill	2 capsules at 730 mg fill	2 capsules at 1100 mg fill	580 mg compound	2 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
375 mg elemental Mg	1,301–1,513 mg compound	3 capsules at 545 mg fill	2–3 capsules at 730 mg fill	2 capsules at 1100 mg fill	622 mg compound	2 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
400 mg elemental Mg	1,387–1,614 mg compound	3 capsules at 545 mg fill	2–3 capsules at 730 mg fill	2 capsules at 1100 mg fill	663 mg compound	2 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
425 mg elemental Mg	1,474–1,715 mg compound	3–4 capsules at 545 mg fill	3 capsules at 730 mg fill	2 capsules at 1100 mg fill	705 mg compound	2 capsules at 545 mg fill	1 capsules at 730 mg fill	1 capsules at 1100 mg fill
450 mg elemental Mg	1,561–1,816 mg compound	3–4 capsules at 545 mg fill	3 capsules at 730 mg fill	2 capsules at 1100 mg fill	746 mg compound	2 capsules at 545 mg fill	2 capsules at 730 mg fill	1 capsules at 1100 mg fill
475 mg elemental Mg	1,648–1,917 mg compound	4 capsules at 545 mg fill	3 capsules at 730 mg fill	2 capsules at 1100 mg fill	787 mg compound	2 capsules at 545 mg fill	2 capsules at 730 mg fill	1 capsules at 1100 mg fill
500 mg elemental Mg	1,734–2,018 mg compound	4 capsules at 545 mg fill	3 capsules at 730 mg fill	2 capsules at 1100 mg fill	829 mg compound	2 capsules at 545 mg fill	2 capsules at 730 mg fill	1 capsules at 1100 mg fill
525 mg elemental Mg	1,821–2,119 mg compound	4 capsules at 545 mg fill	3 capsules at 730 mg fill	2 capsules at 1100 mg fill	870 mg compound	2 capsules at 545 mg fill	2 capsules at 730 mg fill	1 capsules at 1100 mg fill
550 mg elemental Mg	1,908–2,220 mg compound	4–5 capsules at 545 mg fill	3–4 capsules at 730 mg fill	2–3 capsules at 1100 mg fill	912 mg compound	2 capsules at 545 mg fill	2 capsules at 730 mg fill	1 capsules at 1100 mg fill
575 mg elemental Mg	1,994–2,320 mg compound	4–5 capsules at 545 mg fill	3–4 capsules at 730 mg fill	2–3 capsules at 1100 mg fill	953 mg compound	2 capsules at 545 mg fill	2 capsules at 730 mg fill	1 capsules at 1100 mg fill
600 mg elemental Mg	2,081–2,421 mg compound	4–5 capsules at 545 mg fill	3–4 capsules at 730 mg fill	2–3 capsules at 1100 mg fill	995 mg compound	2 capsules at 545 mg fill	2 capsules at 730 mg fill	1 capsules at 1100 mg fill
625 mg elemental Mg	2,168–2,522 mg compound	4–5 capsules at 545 mg fill	3–4 capsules at 730 mg fill	2–3 capsules at 1100 mg fill	1,036 mg compound	2 capsules at 545 mg fill	2 capsules at 730 mg fill	1 capsules at 1100 mg fill
650 mg elemental Mg	2,255–2,623 mg compound	5 capsules at 545 mg fill	4 capsules at 730 mg fill	3 capsules at 1100 mg fill	1,078 mg compound	2 capsules at 545 mg fill	2 capsules at 730 mg fill	1 capsules at 1100 mg fill
675 mg elemental Mg	2,341–2,724 mg compound	5 capsules at 545 mg fill	4 capsules at 730 mg fill	3 capsules at 1100 mg fill	1,119 mg compound	3 capsules at 545 mg fill	2 capsules at 730 mg fill	2 capsules at 1100 mg fill
700 mg elemental Mg	2,428–2,825 mg compound	5–6 capsules at 545 mg fill	4 capsules at 730 mg fill	3 capsules at 1100 mg fill	1,160 mg compound	3 capsules at 545 mg fill	2 capsules at 730 mg fill	2 capsules at 1100 mg fill
725 mg elemental Mg	2,515–2,926 mg compound	5–6 capsules at 545 mg fill	4–5 capsules at 730 mg fill	3 capsules at 1100 mg fill	1,202 mg compound	3 capsules at 545 mg fill	2 capsules at 730 mg fill	2 capsules at 1100 mg fill
750 mg elemental Mg	2,601–3,027 mg compound	5–6 capsules at 545 mg fill	4–5 capsules at 730 mg fill	3 capsules at 1100 mg fill	1,243 mg compound	3 capsules at 545 mg fill	2 capsules at 730 mg fill	2 capsules at 1100 mg fill
775 mg elemental Mg	2,688–3,128 mg compound	5–6 capsules at 545 mg fill	4–5 capsules at 730 mg fill	3 capsules at 1100 mg fill	1,285 mg compound	3 capsules at 545 mg fill	2 capsules at 730 mg fill	2 capsules at 1100 mg fill
800 mg elemental Mg	2,775–3,228 mg compound	6 capsules at 545 mg fill	4–5 capsules at 730 mg fill	3 capsules at 1100 mg fill	1,326 mg compound	3 capsules at 545 mg fill	2 capsules at 730 mg fill	2 capsules at 1100 mg fill
825 mg elemental Mg	2,862–3,329 mg compound	6–7 capsules at 545 mg fill	4–5 capsules at 730 mg fill	3–4 capsules at 1100 mg fill	1,368 mg compound	3 capsules at 545 mg fill	2 capsules at 730 mg fill	2 capsules at 1100 mg fill
850 mg elemental Mg	2,948–3,430 mg compound	6–7 capsules at 545 mg fill	5 capsules at 730 mg fill	3–4 capsules at 1100 mg fill	1,409 mg compound	3 capsules at 545 mg fill	2 capsules at 730 mg fill	2 capsules at 1100 mg fill
875 mg elemental Mg	3,035–3,531 mg compound	6–7 capsules at 545 mg fill	5 capsules at 730 mg fill	3–4 capsules at 1100 mg fill	1,451 mg compound	3 capsules at 545 mg fill	2 capsules at 730 mg fill	2 capsules at 1100 mg fill
900 mg elemental Mg	3,122–3,632 mg compound	6–7 capsules at 545 mg fill	5 capsules at 730 mg fill	3–4 capsules at 1100 mg fill	1,492 mg compound	3 capsules at 545 mg fill	3 capsules at 730 mg fill	2 capsules at 1100 mg fill
925 mg elemental Mg	3,208–3,733 mg compound	6–7 capsules at 545 mg fill	5–6 capsules at 730 mg fill	3–4 capsules at 1100 mg fill	1,533 mg compound	3 capsules at 545 mg fill	3 capsules at 730 mg fill	2 capsules at 1100 mg fill
950 mg elemental Mg	3,295–3,834 mg compound	7–8 capsules at 545 mg fill	5–6 capsules at 730 mg fill	3–4 capsules at 1100 mg fill	1,575 mg compound	3 capsules at 545 mg fill	3 capsules at 730 mg fill	2 capsules at 1100 mg fill
975 mg elemental Mg	3,382–3,935 mg compound	7–8 capsules at 545 mg fill	5–6 capsules at 730 mg fill	4 capsules at 1100 mg fill	1,616 mg compound	3 capsules at 545 mg fill	3 capsules at 730 mg fill	2 capsules at 1100 mg fill
1000 mg elemental Mg	3,469–4,036 mg compound	7–8 capsules at 545 mg fill	5–6 capsules at 730 mg fill	4 capsules at 1100 mg fill	1,658 mg compound	4 capsules at 545 mg fill	3 capsules at 730 mg fill	2 capsules at 1100 mg fill

A whole capsule count describes the minimum number of modelled containers needed to hold compound mass. It does not establish the dimensions, packing density or excipient content of a retail product. The ingredient list and serving statement on each linked record supply the product-specific context.

Declarations against capacity

How each salt's capsule labels distribute

In the 2026-08-10 snapshot, the magnesium carbonate form group has 0 audited capsule labels and the magnesium oxide group has 20; their distributions below use the mass-budget counts stored for each form, at powder density 0.6–0.8 g/mL.

Capsule mass budgets within each form group · 2026-08-10
Salt group	All labels	Audited capsules	Fits 0/00	Needs 000	Exceeds 000
Magnesium carbonate	23	0	0	0	0
Magnesium oxide	124	20	17	3	0

At 2026-08-10, magnesium carbonate has 0 of 0 audited capsule labels at or below 730 mg minimum compound mass per capsule, 0 above 730 mg but at or below 1100 mg, and 0 above 1100 mg. Its other 23 labels have no capsule verdict in this group, either because they are not classified as capsules or because a mass budget is unavailable.

At 2026-08-10, magnesium oxide has 17 of 20 audited capsule labels at or below 730 mg minimum compound mass per capsule, 3 above 730 mg but at or below 1100 mg, and 0 above 1100 mg. Its other 104 labels have no capsule verdict in this group, either because they are not classified as capsules or because a mass budget is unavailable.

The audit divides a label's elemental amount by its assigned salt fraction and serving-unit count. It uses the highest fraction, hence the smallest required mass. A hydration interval can move a nominally fitting label into a larger size at its high-mass end. A result exceeding 000 means the assigned single salt exceeds this fill model even at the low-mass end.

Form groups include names in extracted primary rows, resolved salts and full-record salt mentions, and can overlap; a capsule verdict requires a single assigned salt matching this group. These are counts of label declarations, with the capsule model allocating the fill to the compound. Inspect individual serving statements and assigned salts in the audit register and the linked form pages.

Literature coverage

Which measurements are attached to these salts?

As of the literature review dated 2026-09-11, the supplied study collection associates 2 publications with magnesium carbonate and 12 with magnesium oxide; the combined list contains 12 unique publications, with shared records printed once.

Study-set membership · reviewed 2026-09-11
Salt	Publications	Publication years
Magnesium carbonate	2	2005–2022
Magnesium oxide	12	1990–2026

Membership means that at least one selected salt appears in the study's recorded coverage; it does not mean every paper directly compares this exact pair. In particular, an amino-acid-chelate arm does not establish a chemically defined bisglycinate preparation. Each record below retains its actual design, population, read-out and limits.

Published measurements · peer-reviewed sources

12 published measurements relevant to this pair

The 2026-09-11 literature review links these 12 publications, ordered newest first; study outcomes remain attached to their own experimental conditions.

These entries report what each study measured and on whom. They are not advice, not a ranking, and not a claim about any product on this site. Every reference links to its PubMed record so the original can be read in full.

Randomized, open-label study of the short-term pharmacokinetics of oral magnesium oxide in healthy volunteers.
Scientific reports · 2026 · PMID 42091979
Design
Randomized, open-label pharmacokinetic study in 24 healthy male volunteers aged 18-45 years, equally assigned to a single oral dose of either 750 mg or 2000 mg magnesium oxide.
What it measured
Serum magnesium concentrations at baseline and multiple time points up to 12 hours post-dose (colorimetric assay); pharmacokinetic parameters Cmax, Tmax, and AUC0-12 via non-compartmental analysis; safety via vital signs, laboratory parameters, ECG, and adverse events.
Limits
Male volunteers only, no female data; only two dose levels tested (750 mg, 2000 mg) so dose-proportionality across a wider range is not established; terminal elimination parameters (t1/2, AUC0-infinity, CL/F, MRT) could not be estimated within the 12-hour sampling window; single-dose (not chronic) administration; sample size n=24 (12 per dose group).
Comparative Clinical Study on Magnesium Absorption and Side Effects After Oral Intake of Microencapsulated Magnesium (MAGSHAPE™ Microcapsules) Versus Other Magnesium Sources.
Nutrients · 2024 · PMID 39770988
Design
Double-blind, randomized, cross-over clinical study in 40 healthy women and men. Participants followed a low-magnesium diet for 7 days and fasted 8 hours, then received a single oral dose of each of four products in cross-over fashion: microencapsulated magnesium (Mg-MS / MAGSHAPE), magnesium oxide (MgO), magnesium citrate (Mg-C), and magnesium bisglycinate (Mg-BG). Blood was drawn by digital puncture before dosing (0 h) and at 1, 4, and 6 hours after each product.
What it measured
Plasma magnesium concentration at 0, 1, 4, and 6 hours after oral intake of each of the four products; gastrointestinal side effects (intestinal motility, sensations of gastric heaviness) associated with each product.
Limits
Single-dose exposure per product, not chronic supplementation; sample size n=40; a specific proprietary microencapsulation technology was tested, which may not generalize to other encapsulation methods; plasma magnesium was the only absorption marker used (no urinary or tissue measurement).
Effects of short-term magnesium supplementation on ionized, total magnesium and other relevant electrolytes levels.
Biometals : an international journal on the role of metal ions in biology, biochemistry, and medicine · 2022 · PMID 35041150
Design
Short-term, 10-day supplementation study in 61 healthy young female adults, comparing three magnesium supplement forms: magnesium oxide (powder/granulate), magnesium citrate, and magnesium carbonate (effervescent tablets).
What it measured
Ionized magnesium concentration and its percentage of total magnesium; serum total magnesium concentration; other serum electrolyte levels — each assessed at baseline and after the 10-day intervention.
Limits
Healthy young female adults only, no male or older/deficient populations studied; short 10-day intervention with no longer-term follow-up; three specific product formulations were tested, so results may not generalize to other products of the same salts; the abstract does not report the per-arm breakdown of the 61 participants.
Dose-Dependent Absorption Profile of Different Magnesium Compounds
Biological Trace Element Research · 2020 · PMID 30761462
Design
Absorption of several magnesium compounds profiled across doses rather than at a single dose.
What it measured
Absorption is treated as dose-dependent, so a comparison made at one dose need not hold at another — which is why single-dose head-to-head results disagree.
Limits
Compound coverage and sample size vary by arm; read the paper before carrying any single figure across.
Timeline (Bioavailability) of Magnesium Compounds in Hours: Which Magnesium Compound Works Best?
Biological trace element research · 2019 · PMID 29679349
Design
Single-dose administration of 400 mg/70 kg magnesium as one of five compounds (magnesium sulfate, magnesium oxide, magnesium acetyl taurate, magnesium citrate, magnesium malate) to Sprague Dawley rats, with a control group, followed by time-dependent tissue and serum sampling.
What it measured
Time-dependent magnesium absorption profile (area under the curve) in serum; magnesium tissue penetration and concentration, including brain tissue; behavioral indicators (e.g., anxiety-related behavior) recorded in the animals.
Limits
Animal model (Sprague Dawley rats), not humans — extrapolation of pharmacokinetic and behavioral findings to people is not established; single dose only, no chronic-dosing data; per-compound group sample size is not stated in the abstract; behavioral endpoints were measured only in rodents. The tested acetyl taurate is distinct from the unmodified taurate in the chemistry table.
Comparison of magnesium status using X-ray dispersion analysis following magnesium oxide and magnesium citrate treatment of healthy subjects
Magnesium Research · 2012 · PMID 22433473
Design
Oral magnesium citrate versus magnesium oxide in healthy subjects; intracellular magnesium measured by X-ray dispersion analysis, alongside platelet function.
What it measured
The comparison used intracellular magnesium rather than serum magnesium, which changes what the read-out means.
Limits
Healthy subjects, small sample; intracellular magnesium by X-ray dispersion is not a routine clinical measure.
Study of magnesium bioavailability from ten organic and inorganic Mg salts in Mg-depleted rats using a stable isotope approach
Magnesium Research · 2005 · PMID 16548135
Design
Eighty male Wistar rats fed a magnesium-depleted diet for three weeks, then randomised into ten groups, each receiving a different magnesium salt labelled with a stable isotope.
What it measured
Stable isotopes allow absorption and retention to be traced directly rather than inferred from urine, across ten salts at once — the widest head-to-head comparison in the literature.
Limits
Rats, not people, and magnesium-depleted rats at that: depletion itself raises absorption. The breadth of the comparison is its value; the species is its limit.
Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study
Magnesium Research · 2003 · PMID 14596323
Design
Randomised, double-blind, placebo-controlled parallel study in 46 healthy individuals, 300 mg of elemental magnesium per day, comparing an amino-acid chelate, citrate and oxide.
What it measured
Relative bioavailability of the three preparations was compared at an equal elemental dose.
Limits
46 participants, healthy, 300 mg per day; “amino-acid chelate” is a class rather than one defined compound, so the chelate arm is not a single substance.
Bioavailability of US commercial magnesium preparations
Magnesium Research · 2001 · PMID 11794633
Design
Four commercially available US preparations given to healthy volunteers; bioavailability measured as the increment in urinary magnesium excretion.
What it measured
The study set out to test the claim that organic magnesium salts are more easily absorbed than inorganic ones, using urinary excretion as the read-out.
Limits
Healthy volunteers, small sample, urinary excretion as a proxy for absorption rather than a direct measurement of retention.
Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection
JPEN: Journal of Parenteral and Enteral Nutrition · 1995 · PMID 7815675
Design
Comparison of magnesium diglycinate (a chelate) with magnesium oxide in patients who had undergone ileal resection.
What it measured
The work followed in vitro and in situ findings suggesting diglycinate is absorbed by a different route than inorganic salts, and tested that in patients with impaired absorption.
Limits
Patients after ileal resection are a specific clinical population with poor absorption to begin with; results do not transfer to people with an intact gut.
Magnesium bioavailability from magnesium citrate and magnesium oxide
Journal of the American College of Nutrition · 1990 · PMID 2407766
Design
In vitro solubility of 25 mmol of each salt across hydrochloric acid concentrations mimicking achlorhydric to peak acid secretion, plus in vivo gastrointestinal absorbability.
What it measured
Magnesium oxide was virtually insoluble across the acid range tested, while citrate dissolved; absorbability was then compared in vivo.
Limits
Solubility in a beaker is not absorption in a person; the in vivo arm is small. Published 1990.
Effect of magnesium citrate and magnesium oxide on the crystallization of calcium salts in urine
The Journal of Urology · 1990 · PMID 2299712
Design
Seven normal subjects and four patients with recurrent calcium oxalate stones; 486 mg of magnesium per day for two weeks, taken on an empty stomach and again with food.
What it measured
Taken on an empty stomach, urinary magnesium rose by only 77–79 mg per day out of 486 mg given — and the increase changed when the dose was taken with food.
Limits
Eleven subjects; the endpoint is urinary chemistry in stone formers, not absorption in general. Published 1990.

Magnesium carbonate: trace the filed inputs

8 of 23 labels mentioning magnesium carbonate are shown in brand order from the supplied NIH DSLD records, calculated 2026-09-13. Salt mentions can overlap; only records assigned this single salt enter its capsule audit above.

Filed labels in brand and product order · 8 labels · calculated 2026-09-13
Brand / label	Salt / physical state	Filed serving	Observed item price / EC100
Bairn Biologics Magnesium Plus Raspberry Lemonade FlavorNIH DSLD 230669 · label 2020-07-23	Magnesium carbonatePowder	5.7 Gram(s) (1 level scoop)300 mg elemental magnesium per serving	No published price matched to NIH DSLD 230669; barcode not filed as of 2026-09-13.
BIOVEA Calcium-MagnesiumNIH DSLD 248974 · label 2021-05-22	Magnesium oxideCapsule	3 Vegetarian Capsule(s)500 mg elemental magnesium per serving	$14.99 per container; $0.0361 per 100 mgObserved 2026-09-07 · legacy-verified
CVS Pharmacy Natural Calcium, Magnesium & Zinc USPNIH DSLD 12010 · label 2012-08-24	Magnesium oxideUnknown	1 Caplet(s)133 mg elemental magnesium per serving	No published price matched to barcode 0 50428 06542 6 as of 2026-09-13.
Douglas Laboratories Dyna-Cal Extra-Strength Natural Calcium/Magnesium ComplexNIH DSLD 9831 · label 2012-06-01	Single salt unresolved as of 2026-09-13Tablet or Pill	4 Tablet(s)420 mg elemental magnesium per serving	No published price matched to barcode 3 10539 01579 7 as of 2026-09-13.
Douglas Laboratories Dyna-Cal Extra-Strength Natural Calcium/Magnesium ComplexNIH DSLD 9832 · label 2012-06-01	Single salt unresolved as of 2026-09-13Tablet or Pill	4 Tablet(s)420 mg elemental magnesium per serving	No published price matched to barcode 3 10539 01239 0 as of 2026-09-13.
Family Wellness Calcium, Magnesium & ZincNIH DSLD 76776 · label 2017-07-25	Single salt unresolved as of 2026-09-13Tablet or Pill	1 Tablet(s)133 mg elemental magnesium per serving	No published price matched to barcode 0 32251 02718 5 as of 2026-09-13.
Finest Nutrition Calcium, Magnesium & ZincNIH DSLD 64451 · label 2016-09-22	Single salt unresolved as of 2026-09-13Tablet or Pill	1 Tablet(s)133 mg elemental magnesium per serving	No published price matched to barcode 3 11917 13950 0 as of 2026-09-13.
GNC Magnesium Powder LemonNIH DSLD 243047 · label 2021-01-22	Single salt unresolved as of 2026-09-13Powder	4 Gram(s) (1 Scoop)325 mg elemental magnesium per serving	$22.99 per container; $0.0842 per 100 mgObserved 2026-09-07 · legacy-verified

Open the salt index and linked records to inspect ingredient lists, the source of the assigned salt and dated gaps in price matching.

Magnesium oxide: trace the filed inputs

8 of 124 labels mentioning magnesium oxide are shown in brand order from the supplied NIH DSLD records, calculated 2026-09-13. Salt mentions can overlap; only records assigned this single salt enter its capsule audit above.

Filed labels in brand and product order · 8 labels · calculated 2026-09-13
Brand / label	Salt / physical state	Filed serving	Observed item price / EC100
Adaptogen Research Magnesium Buffered ChelateNIH DSLD 247097 · label 2021-05-22	Single salt unresolved as of 2026-09-13Capsule	2 Capsule(s)300 mg elemental magnesium per serving	No published price matched to barcode 688907 859794 as of 2026-09-13.
Adaptogen Research Magnesium Buffered ChelateNIH DSLD 247098 · label 2021-05-22	Single salt unresolved as of 2026-09-13Capsule	2 Capsule(s)300 mg elemental magnesium per serving	No published price matched to barcode 688907 859800 as of 2026-09-13.
Approved Science Magnesium ComplexNIH DSLD 319784 · label 2024-11-22	Single salt unresolved as of 2026-09-13Capsule	1 Capsule(s)200 mg elemental magnesium per serving	No published price matched to barcode X0039PGF67 as of 2026-09-13.
AvalonX Powered by MDLogic Magnesium 8NIH DSLD 299138 · label 2023-11-22	Single salt unresolved as of 2026-09-13Capsule	2 Capsule(s)500 mg elemental magnesium per serving	$21.99 per container; $0.1466 per 100 mgObserved 2026-09-07 · legacy-verified
Basic Vitamins Magnesium 250 mgNIH DSLD 250165 · label 2021-05-22	Magnesium oxideTablet or Pill	1–2 Tablet(s)250 mg elemental magnesium per serving	$5.39 per container; $0.0216 per 100 mgObserved 2026-09-07 · legacy-provisional
BioSchwartz Magnesium BisglycinateNIH DSLD 228062 · label 2020-06-24	Single salt unresolved as of 2026-09-13Capsule	2 Capsule(s)72 mg elemental magnesium per serving	No published price matched to NIH DSLD 228062; barcode not filed as of 2026-09-13.
BIOVEA Calcium-MagnesiumNIH DSLD 248974 · label 2021-05-22	Magnesium oxideCapsule	3 Vegetarian Capsule(s)500 mg elemental magnesium per serving	$14.99 per container; $0.0361 per 100 mgObserved 2026-09-07 · legacy-verified
BIOVEA Magnesium 200 mgNIH DSLD 249072 · label 2021-05-22	Single salt unresolved as of 2026-09-13Capsule	1 Vegetarian Capsule(s)200 mg elemental magnesium per serving	No published price matched to barcode 8 11079 03132 7 as of 2026-09-13.

Open the salt index and linked records to inspect ingredient lists, the source of the assigned salt and dated gaps in price matching.

Retail observations · after chemistry and evidence

Price observations within each salt

As of 2026-09-13, the published price set contains 0 verified magnesium carbonate matches and 4 verified magnesium oxide matches. Each table below contains one salt and its own sample size; verified medians describe only that salt's verified rows.

EC100 = container price ÷ (declared elemental mg per serving × servings per container ÷ 100). It normalizes the container's elemental amount. The observations use one-time item prices, without coupons or subscriptions and excluding shipping. The tables retain the two salts' page order; sorting operates inside an individual salt table.

Magnesium carbonate: its own retail sample

As of 2026-09-13, magnesium carbonate has 0 verified matches and 0 pending matches in the price set. No verified median is available as of 2026-09-13. Observation dates: No published observations as of 2026-09-13.

0 verified retail matches are published for magnesium carbonate as of 2026-09-13.

There are 0 pending price matches for magnesium carbonate as of 2026-09-13.

Open the magnesium carbonate label group →

Magnesium oxide: its own retail sample

As of 2026-09-13, magnesium oxide has 4 verified matches and 10 pending matches in the price set. Its verified EC100 median is $0.1051 per 100 mg elemental magnesium (n=4); pending matches are excluded from that median. Observation dates: 2026-08-10 to 2026-09-11.

Magnesium oxide · verified observations · reviewed 2026-09-13 · n= 4

Magnesium oxide · verified observations · reviewed 2026-09-13 · n=

Carlson	Magnesium Gels 400 mgNIH DSLD · Label 216334	400 mg	100	$25.42Per container · Price observed 2026-09-07, Amazon	$0.063640.00 total elemental g/container	Verified
AvalonX Powered by MDLogic	Magnesium 8NIH DSLD · Label 299138	500 mg	30	$21.99Per container · Price observed 2026-09-07, Amazon	$0.146615.00 total elemental g/container	Verified
BIOVEA	Calcium-MagnesiumNIH DSLD · Label 248974	500 mg	83	$14.99Per container · Price observed 2026-09-07, Amazon	$0.036141.50 total elemental g/container	Verified
Douglas Laboratories	Magnesix Magnesium And B-6NIH DSLD · Label 26807	50 mg	100	$11.50Per container · Price observed 2026-09-07, Amazon	$0.23005.00 total elemental g/container	Verified

Magnesium oxide · pending observations · reviewed 2026-09-13 · n= 10

These candidate retail-to-label matches remain separate from verified rows and are not included in verified medians.

Magnesium oxide · pending observations · reviewed 2026-09-13 · n=

Nature's Way	Alpha Betic Cinnamon with Magnesium & BiotinNIH DSLD · Label 213757	200 mg	30	$68.43Per container · Price observed 2026-09-07, Amazon	$1.14056.00 total elemental g/container	Pending verification
Solgar	Magnesium with Vitamin B6NIH DSLD · Label 218430	400 mg	33	$16.76Per container · Price observed 2026-08-10, Amazon	$0.127013.20 total elemental g/container	Pending verification
Solgar	Magnesium with Vitamin B6NIH DSLD · Label 218431	400 mg	83	$16.76Per container · Price observed 2026-08-10, Amazon	$0.050533.20 total elemental g/container	Pending verification
Basic Vitamins	Magnesium 250 mgNIH DSLD · Label 250165	250 mg	100	$5.39Per container · Price observed 2026-09-07, Amazon	$0.021625.00 total elemental g/container	Pending verification
DC	Magnesium 500 mgNIH DSLD · Label 267037	500 mg	60	$23.99Per container · Price observed 2026-08-10, Amazon	$0.080030.00 total elemental g/container	Pending verification
DC	Magnesium Oxide 400 mgNIH DSLD · Label 267034	241.3 mg	120	$24.99Per container · Price observed 2026-08-10, Amazon	$0.086328.96 total elemental g/container	Pending verification
BulkSupplements.com	Magnesium Oxide PowderNIH DSLD · Label 329720	500 mg	599	$17.97Per container · Price observed 2026-09-11, Amazon	$0.0060299.50 total elemental g/container	Pending verification
Wonder Labs	Magnesium Oxide 400NIH DSLD · Label 261002	482.6 mg	125	$21.49Per container · Price observed 2026-09-11, Amazon	$0.035660.33 total elemental g/container	Pending verification
Wonder Labs	Magnesium Oxide 400NIH DSLD · Label 262919	482.6 mg	125	$21.49Per container · Price observed 2026-09-11, Amazon	$0.035660.33 total elemental g/container	Pending verification
Wonder Labs	Magnesium Oxide 400NIH DSLD · Label 316129	482.6 mg	125	$21.49Per container · Price observed 2026-09-11, Amazon	$0.035660.33 total elemental g/container	Pending verification

Open the magnesium oxide label group →

To reproduce a container calculation, use the elemental cost calculator and its static mass tables. The magnesium collection abstract connects each salt group to the label corpus; the literature collection puts the cited measurements in their broader study context.