Label arithmetic · NIH DSLD 336940
tnvitamins Magnesium Oxide 420 mg: 420 mg of magnesium per capsule, 1 capsule a day, $3.25 a month
420 mg of magnesium per capsule; the label's 1 capsule a day cost $3.25 a month (Amazon, Nov 2). Inside: salt weight, capsule size, price rank.
tnvitamins Magnesium Oxide 420 mg declares 420 mg of elemental magnesium per serving as oxide, which needs 696 mg of magnesium oxide in each capsule, against 730 mg in a size 00 capsule at powder density 0.8 g/mL, the top of the usual 0.6–0.8 range: it needs size 00 or larger. Observed at $0.0258 per 100 mg, rank 2 of 5 ranked oxide offers (1 = lowest price per 100 mg), percentile 40 (lower = lower price). NIH DSLD 336940, label dated 2025-09-25.
computed from the filed label
Chart data
| Displayed chart text |
|---|
| 545 mg |
| 730 mg |
| 1,100 mg |
| 696 mg of oxide per capsule |
Data release 2026-08-10-f441aa9f · registry snapshot 2026-08-10 · latest price observation 2026-11-02 · chemistry 2026-10-17
Mass: 696 mg per capsule · Price: $0.0258 per 100 mg · % DV: 100% vs 100%
Elemental: The magnesium itself; the rest of the compound weight is the partner molecule.
Compound: The whole salt, such as magnesium glycinate, that must physically fit in the capsule.
Size 000: The largest standard capsule, about 1,100 mg of powder at 0.8 g/mL, the top of the usual 0.6–0.8 range; size 00 holds about 730 mg and size 0 about 545 mg.
Recompute with your price
Enter the price you paid; the declared amount and servings of this label are prefilled, so the result is the cost per 100 mg of elemental magnesium for your bottle.
Same-salt comparison appears here.
Will 420 mg of oxide actually fit in one capsule, or do I need more than one?
Estimated salt mass versus assumed capsule capacity: tnvitamins Magnesium Oxide 420 mg implies 696 mg of magnesium oxide in each capsule to deliver 420 mg of elemental magnesium, against 1,100 mg in the largest standard capsule (size 000) at powder density 0.8 g/mL, the top of the usual 0.6–0.8 range. Verdict: needs size 00, read at the most favourable hydration and the most units per serving.
computed with assumption| Measure | Value |
|---|---|
| Elemental magnesium per serving | 420 mg |
| Units per serving | 1 |
| Magnesium oxide per serving | 696 mg |
| Magnesium oxide per capsule | 696 mg |
| Capsule capacity 0 · 00 · 000 | 545 · 730 · 1,100 mg |
| Verdict | Needs size 00 |
Source · NIH DSLD 336940 · label 2025-09-25; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
How much elemental magnesium is actually in this label's filed magnesium lines?
tnvitamins Magnesium Oxide 420 mg files 1 magnesium line in NIH DSLD 336940; the selected primary line declares 420 mg of elemental magnesium per serving, against 0 other rows excluded from the primary amount. A salt named under another nutrient does not turn that nutrient's quantity into elemental magnesium.
measured| Filed amount | Salt or note as filed | Role |
|---|---|---|
| 420 mg | from | Primary serving |
Source · NIH DSLD 336940 · label 2025-09-25; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
Does this label's oxide claim hold up, or could the magnesium come from another source?
The label names one magnesium form, oxide, resolved from the full NIH DSLD record text; at that salt the declaration is within the assumed size 000 capacity at powder density 0.8 g/mL, compared with oxide, the salt richest in magnesium at 60.3%.
computed with assumption| Form named on the label | Elemental fraction | Source |
|---|---|---|
| Magnesium oxide | 60.3% | full NIH DSLD record text |
Source · NIH DSLD 336940 · label 2025-09-25; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
Is this a good price for the elemental magnesium I'm actually getting?
tnvitamins Magnesium Oxide 420 mg costs $0.0258 per 100 mg of elemental magnesium at the price observed 2026-11-02, rank 2 of 5 ranked oxide offers (1 = lowest price per 100 mg), percentile 40 (lower = lower price), against a same-salt median of $0.0293; prices observed 2026-10-26 to 2026-11-02. First observed 2026-10-19 at $12.99, latest 2026-11-02 at $12.99, 3 observations.
computed
Chart data
| Displayed chart text |
|---|
| n=5 |
| P25 $0.0258 |
| P75 $0.0356 |
| median $0.0293 |
| Rank | Label | Per 100 mg | Observed |
|---|---|---|---|
| 1 | Nutricost Magnesium Oxide | $0.0148 | 2026-11-02 |
| 2 | tnvitamins Magnesium Oxide 420 mg | $0.0258 | 2026-11-02 |
| 3 | Douglas Laboratories Magnesium Oxide | $0.0293 | 2026-11-02 |
| 4 | Wonder Labs Magnesium Oxide 400 | $0.0356 | 2026-11-02 |
| 5 | Carlson Magnesium Gels 400 mg | $0.0636 | 2026-11-02 |
| Median | 5 ranked oxide offers | $0.0293 | 2026-11-02 |
Source · Amazon via licensed data provider; NIH DSLD · unique ASIN × date; prices observed 2026-10-26 to 2026-11-02 · release 2026-08-10-f441aa9f · CSV · method
How many days will this bottle last at the label's own serving, and what does a day cost?
At the label's own serving, tnvitamins Magnesium Oxide 420 mg lasts 120 days: 120 servings against 1 serving a day in the filed directions. $3.25 a month at the label's suggested use (1 capsule a day) and $3.25 at the 420 mg Daily Value reference (21 CFR 101.9); arithmetic on the label, not intake advice.
computed| Measure | Value |
|---|---|
| Net contents as filed | 120 Capsule(s) |
| Serving size as filed | 1 Capsule(s) |
| Servings per container | 120 |
| Servings per day in the directions | 1 |
| Days per bottle | 120 days |
| Cost a month at the label suggested use | $3.25 a month at the label's suggested use (1 capsule a day) |
| $ per 30 days at 420 mg Daily Value | $3.25 |
Source · NIH DSLD 336940 · label 2025-09-25; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
What does "100% Daily Value" mean here, and does it recompute?
The label declares 100% Daily Value; 420 mg against the 420 mg reference in 21 CFR 101.9 recomputes to 100%, the same within one point.
computed| Group as filed | Declared | Reference | Recomputed |
|---|---|---|---|
| Adults and children 4 or more years of age | 100% | 420 mg | 100% |
Source · NIH DSLD 336940; 21 CFR 101.9 · label 2025-09-25 · release 2026-08-10-f441aa9f · CSV · method
Why does this label contain magnesium stearate, what shell is it, and who is it filed for?
tnvitamins Magnesium Oxide 420 mg files 3 other ingredients, including magnesium stearate (reference fraction 4.1% magnesium; no quantity filed, so it is not added to the total) and a gelatin shell, against 30 of 61 oxide labels that list magnesium stearate.
measured| Entry | Filed ingredient or declaration |
|---|---|
| 1 | Microcrystalline Cellulose |
| 2 | Magnesium Stearate |
| 3 | Gelatin |
| Shell | gelatin |
| Target group | Adult (18 - 50 Years) |
| Target group | No Allergies |
| Target group | Gluten Free |
| Target group | Dairy Free |
Source · NIH DSLD 336940 · label 2025-09-25; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
What has research measured about oxide, and about side effects?
12 studies in the PubMed-checked registry measured outcomes involving oxide; 2 mention gastrointestinal or adverse outcomes. They measured the salt, not this label.
measured| Year | Study | PubMed |
|---|---|---|
| 2026 | Randomized, open-label study of the short-term pharmacokinetics of oral magnesium oxide in healthy volunteers. | 42091979 |
| 2024 | Comparative Clinical Study on Magnesium Absorption and Side Effects After Oral Intake of Microencapsulated Magnesium (MAGSHAPE™ Microcapsules) Versus Other Magnesium Sources. | 39770988 |
| 2022 | Effects of short-term magnesium supplementation on ionized, total magnesium and other relevant electrolytes levels. | 35041150 |
Source · PubMed-checked study registry · registry checked 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
Has this brand had FDA recalls or adverse event reports?
tnvitamins has 2 FDA recall records matched by brand name in the enforcement data queried 2026-10-19. tnvitamins has no FDA CAERS adverse event report on record at brand level as of 2026-10-19 (143 of 273 brands in this registry have at least one CAERS report).
measured| Recall | Date | Reason | Status |
|---|---|---|---|
| H-0942-2026 | 2026-06-17 | Product may be contaminated with Salmonella. | Ongoing |
| H-1185-2026 | 2026-07-29 | Contaminated with Salmonella | Ongoing |
Source · openFDA enforcement and CAERS · queried 2026-10-19 · release 2026-08-10-f441aa9f · CSV · method
Is this the same formula as another brand's, and how do their prices differ?
No other brand files the same formulation (ingredients, shell, units and rounded amount) as of 2026-11-02.
computed| Label | Brand | Price per 100 mg |
|---|---|---|
| No cross-brand match as of 2026-11-02 |
Source · NIH DSLD 336940 · label 2025-09-25; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
Which labels are closest to this one, with the same salt and dose?
5 labels use the same resolved oxide within ±10% of this label's 420 mg per unit, compared side by side on price and capsule verdict.
computed| Label | Elemental per unit | Price | Verdict |
|---|---|---|---|
| Nutricost Magnesium Oxide | 420 mg | $14.95 · 2026-11-02 | Needs size 00 |
| Finest Nutrition Magnesium 400 mg | 400 mg | No price | Capsule sizes do not apply |
| Nature Made High Potency Magnesium 400 mg | 400 mg | No price | Capsule sizes do not apply |
| Carlson Magnesium Gels 400 mg (DSLD 216334) | 400 mg | $25.42 · 2026-11-02 | Capsule sizes do not apply |
| Carlson Magnesium Gels 400 mg (DSLD 216338) | 400 mg | No price | Capsule sizes do not apply |
Source · NIH DSLD 336940 · label 2025-09-25; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
Where does this record come from, what is missing, and how do I cite or correct it?
Every value on this page traces to NIH DSLD 336940 (label 2025-09-25, snapshot 2026-08-10), a price observed 2026-11-02 and the chemistry model of 2026-09-13. No data gap remains for the computed fields. The CSV carries the values shown here.
measured| Field | As filed |
|---|---|
| NIH DSLD label | NIH DSLD 336940 |
| Scanned label (PDF) | Label 336940 scan |
| Label date | 2025-09-25 |
| Date entered into DSLD | 2025-09-25 |
| Barcode (UPC) as filed | X004C81D49 |
| Manufactured and Laboratory Tested for | Total Nutrition Inc., Deer Park, NY, USA |
| Claim category as filed | Nutrient |
| Claim category as filed | All Other |
12 additional rows
| Field | As filed |
|---|---|
| Suggested/Recommended/Usage/Directions | Directions: As a dietary supplement for adults, take one (1) capsule daily, or as directed by a healthcare professional. |
| Precautions re: Pregnant or Nursing or Prescription Medications | Caution: pregnant or lactating women should consult a doctor before use. |
| Precautions re: All Other | If you are under medical supervision, please consult a doctor before use. Discontinue use and consult a doctor if any adverse reactions occur. |
| Precautions re: Children | Keep out of reach of children. |
| Storage | Store in a cool, dry place. |
| Formula re: Contains | Magnesium Oxide 420 mg per capsule |
| Formulation re: Does NOT Contain | Free of: Gluten, peanuts, tree nuts, sesame, dairy (milk, eggs), fish, crustaceans, soy, wheat, corn, artificial colors, flavors, or preservatives. GMO free |
| Seals/Symbols | Made in the USA Manufactured in GMP Certified Facilities FDA Compliant |
| General Statements: All Other Content | New |
| FDA Statement of Identity | Dietary Supplement |
| Physical state | Capsule |
| Registry snapshot | 2026-08-10 |
Source · NIH DSLD 336940 · label 2025-09-25; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
6 brand pages linked below contain magnesium labels from the NIH DSLD registry snapshot dated 2026-08-10.