Label arithmetic · NIH DSLD 245309
Douglas Laboratories Magnesium Oxide: 300 mg of magnesium per capsule, 1 capsule a day, $2.64 a month
300 mg of magnesium per capsule; the label's 1 capsule a day cost $2.64 a month (Amazon, Nov 2). Inside: salt weight, capsule size, price rank.
Douglas Laboratories Magnesium Oxide was observed at $22.00 on 2026-11-02 for 250 servings of 300 mg elemental magnesium as oxide: $0.0293 per 100 mg, rank 3 of 5 ranked oxide offers (1 = lowest price per 100 mg), percentile 60 (lower = lower price) (median $0.0293, ranked prices observed 2026-10-26 to 2026-11-02). NIH DSLD 245309, label dated 2021-02-25.
computed from the filed label
Chart data
| Displayed chart text |
|---|
| 545 mg |
| 730 mg |
| 1,100 mg |
| 497 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: 497 mg per capsule · Price: $0.0293 per 100 mg · % DV: 71% vs 71%
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 300 mg of oxide actually fit in one capsule, or do I need more than one?
Estimated salt mass versus assumed capsule capacity: Douglas Laboratories Magnesium Oxide implies 497 mg of magnesium oxide in each capsule to deliver 300 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: fits size 0, read at the most favourable hydration and the most units per serving.
computed with assumption| Measure | Value |
|---|---|
| Elemental magnesium per serving | 300 mg |
| Units per serving | 1 |
| Magnesium oxide per serving | 497 mg |
| Magnesium oxide per capsule | 497 mg |
| Capsule capacity 0 · 00 · 000 | 545 · 730 · 1,100 mg |
| Verdict | Fits size 0 |
Source · NIH DSLD 245309 · label 2021-02-25; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
How much elemental magnesium is actually in this label's filed magnesium lines?
Douglas Laboratories Magnesium Oxide files 1 magnesium line in NIH DSLD 245309; the selected primary line declares 300 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 |
|---|---|---|
| 300 mg | oxide · Magnesium (Form: from 500 mg Magnesium Oxide) | Primary serving |
Source · NIH DSLD 245309 · label 2021-02-25; 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 filed magnesium line; 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% | filed magnesium line |
Source · NIH DSLD 245309 · label 2021-02-25; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
Is this a good price for the elemental magnesium I'm actually getting?
Douglas Laboratories Magnesium Oxide costs $0.0293 per 100 mg of elemental magnesium at the price observed 2026-11-02, rank 3 of 5 ranked oxide offers (1 = lowest price per 100 mg), percentile 60 (lower = lower price), against a same-salt median of $0.0293; prices observed 2026-10-26 to 2026-11-02. First observed 2026-10-26 at $22.00, latest 2026-11-02 at $22.00, 2 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, Douglas Laboratories Magnesium Oxide lasts 250 days: 250 servings against 1 serving a day in the filed directions. $2.64 a month at the label's suggested use (1 capsule a day) and $3.69 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 | 250 Vegetarian Capsule(s) |
| Serving size as filed | 1 Vegetarian Capsule(s) |
| Servings per container | 250 |
| Servings per day in the directions | 1 |
| Days per bottle | 250 days |
| Cost a month at the label suggested use | $2.64 a month at the label's suggested use (1 capsule a day) |
| $ per 30 days at 420 mg Daily Value | $3.69 |
Source · NIH DSLD 245309 · label 2021-02-25; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
What does "71% Daily Value" mean here, and does it recompute?
The label declares 71% Daily Value; 300 mg against the 420 mg reference in 21 CFR 101.9 recomputes to 71%, the same within one point.
computed| Group as filed | Declared | Reference | Recomputed |
|---|---|---|---|
| Adults and children 4 or more years of age | 71% | 420 mg | 71% |
Source · NIH DSLD 245309; 21 CFR 101.9 · label 2021-02-25 · release 2026-08-10-f441aa9f · CSV · method
Why does this label contain these other ingredients, what shell is it, and who is it filed for?
Douglas Laboratories Magnesium Oxide files 6 other ingredients and a vegetarian shell, and no magnesium stearate, against 30 of 61 oxide labels that list magnesium stearate.
measured| Entry | Filed ingredient or declaration |
|---|---|
| 1 | Hydroxypropyl Methylcellulose |
| 2 | Microcrystalline Cellulose |
| 3 | Carnauba wax |
| 4 | Ascorbyl Palmitate |
| 5 | Hydroxypropyl Cellulose |
| 6 | Silica |
| Shell | vegetarian |
| Target group | Adult (18 - 50 Years) |
1 additional rows
| Entry | Filed ingredient or declaration |
|---|---|
| Target group | Gluten Free |
Source · NIH DSLD 245309 · label 2021-02-25; 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?
Douglas Laboratories has 1 FDA recall record matched by brand name in the enforcement data queried 2026-10-19. Douglas Laboratories has FDA CAERS adverse event reports on record at brand level, as do 143 of 273 brands in this registry; openFDA states that “there is no certainty that the reported event (adverse event) was actually due to the product” and that reports “cannot be used to estimate the incidence of these events.”
measured| Recall | Date | Reason | Status |
|---|---|---|---|
| F-1202-2015 | 2015-02-18 | Bottles contained a vegetarian digestive enzyme dietary supplement instead of melatonin. | Terminated |
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?
Same filed formulation as 1 other labels of this brand; no other brand files it as of 2026-11-02.
computed| Label | Brand | Price per 100 mg |
|---|---|---|
| No cross-brand match as of 2026-11-02 |
Source · NIH DSLD 245309 · label 2021-02-25; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
Which labels are closest to this one, with the same salt and dose?
3 labels use the same resolved oxide within ±10% of this label's 300 mg per unit, compared side by side on price and capsule verdict.
computed| Label | Elemental per unit | Price | Verdict |
|---|---|---|---|
| Dr. Clark Store Magnesium 300 mg (DSLD 215070) | 300 mg | No price | Fits size 0 |
| Dr. Clark Store Magnesium 300 mg (DSLD 215806) | 300 mg | No price | Fits size 0 |
| Douglas Laboratories Magnesium Oxide | 300 mg | No price | Fits size 0 |
Source · NIH DSLD 245309 · label 2021-02-25; 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 245309 (label 2021-02-25, 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 245309 |
| Label date | 2021-02-25 |
| Date entered into DSLD | 2021-02-25 |
| Barcode (UPC) as filed | 3 10539 97834 4 |
| Label version · Image difference, same product | NIH DSLD 230475 |
| Label version · Package size difference, same product | NIH DSLD 230473 |
| Label version · Package size difference, same product | NIH DSLD 232875 |
| Label version · Package size difference, same product | NIH DSLD 230475 |
14 additional rows
| Field | As filed |
|---|---|
| Manufactured by | Douglas Laboratories, Pittsburgh, PA |
| Claim category as filed | All Other |
| Claim category as filed | Structure/Function |
| Suggested/Recommended/Usage/Directions | Suggested Usage: As a dietary supplement, adults take 1 capsule daily or as directed by your health professional. |
| Precautions re: Pregnant or Nursing or Prescription Medications | Warning: If you are pregnant, or nursing, or if you are taking prescription medication, consult your health professional before using this product. |
| Precautions re: Children | Keep out of the reach of children. |
| Storage | Store in a cool, dry place. |
| Precautions re: All Other | Use only if safety seal is intact. |
| Formulation re: Does NOT Contain | Gluten-free, Non-GMO |
| FDA Disclaimer Statement | This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. |
| General Statements: All Other Content | Contents may not fill package in order to accommodate required labeling. Please rely on stated quantity. Scan to learn about our manufacturing excellence |
| FDA Statement of Identity | Dietary Supplement |
| Physical state | Capsule |
| Registry snapshot | 2026-08-10 |
Source · NIH DSLD 245309 · label 2021-02-25; 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.