Read the elemental magnesium figure on the Supplement Facts panel, not the compound weight on the front; divide it by the compound weight to check the form is what the label says; count the capsules per serving; and add every source you take, keeping supplemental magnesium under 350 mg a day. Prefer a form named outright, and a certificate that says what it did and did not measure.
A magnesium label carries two honest numbers that differ several-fold, and most of the buying decision is knowing which one to read. The six checks below are about getting the dose you think you are getting; none of them is an argument that one form does more for a body than another, and this page makes no such claim. The arithmetic behind the elemental figure is worked through in elemental magnesium, and how to read a label; whether a man who lifts needs magnesium at all is answered in supplements for men over 45 who lift.
| What to check | What good looks like | The red flag |
|---|---|---|
| Elemental figure | Magnesium in mg, with the source in brackets: “Magnesium (as magnesium glycinate)” | Only a compound weight, front or back |
| The division | Elemental ÷ compound at or under the named form’s ceiling: glycinate 14.1%, oxide 60.3% | A glycinate that divides out above 14.1% |
| Capsule count | Capsules per serving and servings per bottle that match the dose taken | A capsule count read as a day count |
| Your total | Every supplemental source added, under 350 mg a day | A second product whose magnesium nobody counted |
| Buffered blend | Every source named on the panel | “Glycinate” on the front and a second source, or none, behind it |
| Certificate | A magnesium figure with the sample and serving stated, plus an identity test | An elemental magnesium row presented as proof of the form |
What is the best form of magnesium to take daily?
No form is best on the evidence, and the label can show the trade-off. The NIH Office of Dietary Supplements reports that small studies found the aspartate, citrate, lactate and chloride forms absorbed more completely than oxide and sulfate, and that forms which dissolve well in liquid absorb better. Oxide packs the most magnesium into a gram; a chelate such as glycinate packs far less, which is why it needs more capsules for the same dose.
Each pairing has its own page: glycinate vs oxide, glycinate vs citrate, glycinate vs malate, chloride vs glycinate and threonate vs glycinate, with all of them side by side on the supplement forms hub and the trials in the magnesium research summary.
How do you read the elemental magnesium on a label?
Find the line that reads like “Magnesium (as magnesium glycinate) 200 mg”: that number is elemental magnesium, the weight of the mineral itself. A figure printed against the compound name alone, such as “magnesium glycinate 1,420 mg”, is the weight of the whole salt. The NIH Office of Dietary Supplements says the panel “declares the amount of elemental magnesium in the product, not the weight of the entire magnesium-containing compound,” and the FDA’s labelling guide applies the same rule to calcium.
The front of a bottle is a design decision, and a larger compound figure, where one is printed, does its work there. Read the panel, and use the elemental number for every sum on this page. The same reading, line by line for any supplement, is in how to read a supplement label, and every term in the supplement label glossary.
How can you tell if a magnesium glycinate is buffered?
Divide. Pure magnesium glycinate, C4H8MgN2O4 in PubChem’s entry, is 14.1% magnesium by weight on arithmetic from its formula, and magnesium oxide, MgO, is 60.3%. So a glycinate panel’s elemental figure divided by the compound weight beside it should not come out above 14.1%. If it does, some of the magnesium is coming from something denser, such as oxide. The division is a hint, not a test: it catches a label that does not add up and misses one that does.
Disclosure is the other half. The FDA’s labelling guide requires the weight of the mineral and lets a brand name its sources in the panel, and its answer on sources asks for no weight per source. So a panel reading “Magnesium (as magnesium glycinate, magnesium oxide)” can meet that rule and still not say how much of each. A buffered product is a legitimate manufacturing choice when it is named as a blend; the red flag is the word glycinate on the front and an unnamed second source behind it. More in magnesium bisglycinate vs glycinate.
How many capsules of magnesium should a serving take?
As many as the elemental dose needs, and a chelate needs more than oxide. Divide the elemental figure per serving by the capsules per serving to get magnesium per capsule, then divide the bottle’s capsule count by the capsules per serving to get days: a 90-capsule bottle at three a serving is 30 days, not 90. Because pure glycinate is 14.1% magnesium, every gram of magnesium needs about 7.1 g of compound to carry it.
That last figure turns the capsule count into a check rather than a nuisance. By the same arithmetic, 1,000 mg of pure glycinate holds at most 141 mg of magnesium, so one capsule printing 300 mg of magnesium from glycinate alone would need more than 2 g of compound inside it.
How much magnesium from supplements is too much?
More than 350 mg a day from supplements and medicines combined, for adults: that is the upper level the NIH Office of Dietary Supplements gives, and magnesium from food and drink does not count toward it. The office notes that high doses from supplements or medicines often cause diarrhoea. The number to add up is the elemental magnesium from every product taken, not the compound weights, and not one bottle on its own.
Magnesium turns up in products that are not sold as magnesium. One magnesium-based laxative supplies 500 mg of elemental magnesium per tablespoon and one extra-strength antacid 55 mg a tablet (ODS). When Clemesha and colleagues audited 50 products sold as testosterone boosters, 13 went over the upper intake level for zinc, vitamin B3 or magnesium. Two numbers get confused here, and they count different things: the RDA of 420 mg for men 31 and over counts food, drink and supplements together, while the 350 mg upper level counts only supplements and medicines (ODS). A man who eats 300 mg and takes 300 mg meets the first and stays under the second. Read every panel in the cabinet before adding a magnesium product; the ceiling is worked through in can you take too much magnesium, and the daily figures in how much magnesium per day.
What can a certificate of analysis tell you about magnesium?
How much magnesium was in the sample, and nothing about which compound carried it. If the magnesium row names ICP-MS, it is an elemental method: the FDA’s own ICP-MS method for elements in food begins by decomposing the sample in acid under microwave heat, then reports total acid-extractable concentrations of the elements it covers. The compound is broken down before the count, so that row would read the same for glycinate, oxide or citrate. Only an identity test can say which.
Two more fields decide what the figure means. The sample: raw-material powder in a sack, or a finished capsule. And the serving: a laboratory’s serving need not be the label’s, and a figure per laboratory serving multiplied up to a capsule count is arithmetic, not a measurement. The full reading is in what is a certificate of analysis, and the three different checks one badge word can stand for in their own explainer.
What the research does not show
It does not rank forms for people in any precise way. The absorption comparisons the NIH office cites are small studies; they say some forms are absorbed more completely than oxide and sulfate, not how much that difference matters at a given dose.
It does not make the ceilings a test. The 14.1% and 60.3% are arithmetic on pure compounds. Real ingredients can carry water or other material, so a glycinate can land under its ceiling for innocent reasons, and the division only flags a figure above it.
It does not let a blood test settle the question of need: the office notes that serum levels do not accurately reflect the body’s total magnesium. And it does not let an elemental assay vouch for a form. A certificate without an identity test cannot say what the magnesium was bound to.
Nor does any of this support an outcome claim for one form over another. The checks above are about dose and disclosure, and the evidence for each form is in the magnesium research summary; the side effects and the ceiling are in magnesium glycinate side effects.
Where Night Work sits against these checks
Night Work is magnesium glycinate in capsules: 275 mg of elemental magnesium from 2,500 mg of magnesium glycinate per three-capsule serving, as the label states it, 30 servings in a 90-capsule bottle. By the division above, 275 ÷ 2,500 is 11.0%, under the 14.1% ceiling, which says the panel adds up and not what the capsule holds. It is the only supplemental magnesium in the TARE range: 275 mg, 75 mg under the 350 mg upper level. Its certificate is from Ethos Analytics, issued for Vox Nutrition on raw-material lot MGL260212 and completed on 24 February 2026. The magnesium document covers a raw-material powder lot: it carries a measured magnesium figure, a heavy-metal panel and a microbiological panel for that powder, and no identity test, so it still cannot vouch for what is in the capsule. Its figure is 102.54 mg of magnesium per 926 mg laboratory serving against a 91.6 mg specification, and the powder passed both panels; that serving is the laboratory’s and not the label’s three capsules, and the document does not test a TARE container. Every row is on Testing & Certification.
The same checks for the other two ingredients are in how to choose a creatine supplement and how to choose a collagen supplement, with their evidence in the creatine research summary and the collagen research summary.
Sources
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals (updated 6 January 2026). NIH Office of Dietary Supplements
- US Food and Drug Administration. Dietary Supplement Labeling Guide: Chapter IV. Nutrition Labeling (2005). fda.gov
- PubChem. Magnesium glycinate, CID 84645 (molecular formula C4H8MgN2O4). pubchem.ncbi.nlm.nih.gov
- PubChem. Magnesium oxide, CID 14792 (molecular formula MgO). pubchem.ncbi.nlm.nih.gov
- Gray PJ, Mindak WR, Cheng J. FDA Elemental Analysis Manual, section 4.7: ICP-MS determination of elements in food using microwave assisted digestion, version 1.2 (2020). fda.gov
- Clemesha CG, Thaker H, Samplaski MK. World J Mens Health 2020;38(1):115–122. PubMed 31385468