Label arithmetic · NIH DSLD 274903
Source Naturals Magtein Magnesium L-Threonate 667 mg: 49 mg of magnesium per capsule, 3 capsules a day
49 mg of magnesium per capsule; the label's 3 capsules a day give 147 mg. No US price matched (Nov 2). Inside: salt weight, capsule size.
Source Naturals Magtein Magnesium L-Threonate 667 mg declares 147 mg of elemental magnesium per serving as l-threonate, which needs 594 mg of magnesium l-threonate 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. No US retail price matched as of 2026-11-02; 2 of the 8 l-threonate labels in this registry have a matched price. NIH DSLD 274903, label dated 2022-09-22.
computed from the filed label
Chart data
| Displayed chart text |
|---|
| 545 mg |
| 730 mg |
| 1,100 mg |
| 594 mg of l-threonate per capsule |
Data release 2026-08-10-f441aa9f · registry snapshot 2026-08-10 · latest price observation 2026-10-19 · chemistry 2026-10-17
Mass: 594 mg per capsule · Price: none matched · % DV: 35% vs 35%
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 147 mg of l-threonate actually fit in one capsule, or do I need more than one?
Estimated salt mass versus assumed capsule capacity: Source Naturals Magtein Magnesium L-Threonate 667 mg implies 594 mg of magnesium l-threonate in each capsule to deliver 147 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 | 147 mg |
| Units per serving | 3 |
| Magnesium l-threonate per serving | 1,782 mg |
| Magnesium l-threonate per capsule | 594 mg |
| Capsule capacity 0 · 00 · 000 | 545 · 730 · 1,100 mg |
| Verdict | Needs size 00 |
Source · NIH DSLD 274903 · label 2022-09-22; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
How much elemental magnesium is actually in this label's filed magnesium lines?
Source Naturals Magtein Magnesium L-Threonate 667 mg files 1 magnesium line in NIH DSLD 274903; the selected primary line declares 147 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 |
|---|---|---|
| 147 mg | Salt not named in this row; magnesium l-threonate is taken from the label text | Primary serving |
Source · NIH DSLD 274903 · label 2022-09-22; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
Does this label's l-threonate claim hold up, or could the magnesium come from another source?
The label names one magnesium form, l-threonate, 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 L-threonate | 8.3% | full NIH DSLD record text |
Source · NIH DSLD 274903 · label 2022-09-22; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
Is this a good price for the elemental magnesium I'm actually getting?
No US retail price is matched to this label as of 2026-11-02; 2 of 8 l-threonate labels have one, against a median of $1.1572 per 100 mg among 1 ranked l-threonate offer.
computed
Chart data
| Displayed chart text |
|---|
| n=1 |
| median $1.1572 |
| Rank | Label | Per 100 mg | Observed |
|---|---|---|---|
| 1 | Momentous Magnesium Threonate | $1.1572 | 2026-11-02 |
| Median | 1 ranked l-threonate offer | $1.1572 | 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, Source Naturals Magtein Magnesium L-Threonate 667 mg lasts 60 days: 60 servings against 1 serving a day in the filed directions.
computed| Measure | Value |
|---|---|
| Net contents as filed | 180 Capsule(s) |
| Serving size as filed | 3 Capsule(s) |
| Servings per container | 60 |
| Servings per day in the directions | 1 |
| Days per bottle | 60 days |
| $ per 30 days at one label serving a day | No ranked price as of 2026-11-02 |
| $ per 30 days at 420 mg Daily Value | No ranked price as of 2026-11-02 |
Source · NIH DSLD 274903 · label 2022-09-22; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
What does "35% Daily Value" mean here, and does it recompute?
The label declares 35% Daily Value; 147 mg against the 420 mg reference in 21 CFR 101.9 recomputes to 35%, the same within one point.
computed| Group as filed | Declared | Reference | Recomputed |
|---|---|---|---|
| Adults and children 4 or more years of age | 35% | 420 mg | 35% |
Source · NIH DSLD 274903; 21 CFR 101.9 · label 2022-09-22 · release 2026-08-10-f441aa9f · CSV · method
Why does this label contain magnesium stearate, what shell is it, and who is it filed for?
Source Naturals Magtein Magnesium L-Threonate 667 mg files 4 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 1 of 8 l-threonate labels that list magnesium stearate.
measured| Entry | Filed ingredient or declaration |
|---|---|
| 1 | Gelatin |
| 2 | Maltodextrin |
| 3 | Magnesium Stearate |
| 4 | Silica |
| Shell | gelatin |
| Target group | Adult (18 - 50 Years) |
| Target group | Gluten Free |
| Target group | Dairy Free |
Source · NIH DSLD 274903 · label 2022-09-22; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
What has research measured about l-threonate, and about side effects?
No study in the registry measured l-threonate as of 2026-11-02.
measured| Year | Study | PubMed |
|---|
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?
Source Naturals has 6 FDA recall records matched by brand name in the enforcement data queried 2026-10-19. Source Naturals 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-0100-2014 | 2013-11-13 | The firm found small piece of metal fragment in one tablet during its inspection process. | Terminated |
| F-1100-2014 | 2013-12-25 | Dietary Supplements were made with bulk products provided by National Enzyme Company which are currently under recall for chloramphenicol | Terminated |
| F-2178-2017 | 2017-05-10 | Testing of Vitamin D-3 as a result of a consumer complaint found specific lots to have lower concentrations than product specifications of ingredient labeling. | Terminated |
| F-2380-2017 | 2017-07-19 | Dietary supplements contain low levels of undeclared boron | Terminated |
| F-2383-2017 | 2017-07-19 | Dietary supplements contain low levels of undeclared boron | 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?
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 274903 · label 2022-09-22; 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 l-threonate within ±10% of this label's 49 mg per unit, compared side by side on price and capsule verdict.
computed| Label | Elemental per unit | Price | Verdict |
|---|---|---|---|
| Dr. Mercola Magnesium Advanced | 48 mg | $34.97 · 2026-09-21 | Needs size 00 |
| The Vitamin Shoppe Magnesium Threonate | 48 mg | No price | Needs size 00 |
| Momentous Magnesium Threonate | 48 mg | $49.99 · 2026-11-02 | Needs size 00 |
Source · NIH DSLD 274903 · label 2022-09-22; 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 274903 (label 2022-09-22, snapshot 2026-08-10) and the chemistry model of 2026-09-13. 1 gap remain: No US retail price matched as of 2026-11-02 (barcode 0 21078 02486 6). The CSV carries the values shown here.
measured| Field | As filed |
|---|---|
| NIH DSLD label | NIH DSLD 274903 |
| Scanned label (PDF) | Label 274903 scan |
| Label date | 2022-09-22 |
| Date entered into DSLD | 2022-09-22 |
| Barcode (UPC) as filed | 0 21078 02486 6 |
| Label version · Image difference, same product | NIH DSLD 295978 |
| Manufactured for | Source Naturals, Inc., Santa Cruz, CA |
| Claim category as filed | Nutrient |
18 additional rows
| Field | As filed |
|---|---|
| Claim category as filed | All Other |
| Claim category as filed | Structure/Function |
| Formula re: Contains | Magnesium L-Threonate 667 mg |
| Formulation re: Other | For learning and memory |
| Suggested/Recommended/Usage/Directions | Suggested Use: 3 capsules daily, preferably in divided doses. Start with 1 capsule daily and gradually increase to 3 capsules daily. |
| Precautions re: Pregnant or Nursing or Prescription Medications | Caution: Not recommended for use by children or women who are pregnant, may become pregnant, or breastfeeding. If you are taking any prescription drugs, consult your health care professionals before using this product. |
| Precautions re: Children | Caution: Not recommended for use by children or women who are pregnant, may become pregnant, or breastfeeding. |
| Storage | Store in a cool, dry place. |
| Precautions re: All Other | Do not use if either tamper-evident seal is broken or missing. |
| Precautions re: Children | Keep out of the reach of children. |
| Formula re: Contains | Magnesium (Mg) plays an essential role in supporting cognitive function and brain health. Preliminary research suggests that Magtein (magnesium L-threonate) may provide more magnesium to the brain than other forms of magnesium. In preclinical studies, Magtein was shown to support healthy memory and learning as well as healthy brain synapse density in regions of the brain associated with memory. These preclinical findings have now been validated by a clinical study showing positive results in tests of overall cognitive ability after 12 weeks' use of magnesium threonate. |
| Formulation re: Does NOT Contain | Contains no yeast, dairy, egg, gluten, soy or wheat. Contains no preservatives, or artificial color, flavor or fragrance. |
| Brand IP Statement(s) re: (c), (TM), (SM) | Magtein Think Clearly is protected by registered and pending U.S. Patents; is a registered trademark of Magceutics, Inc. and is distributed exclusively by AIDP, INC. |
| FDA Disclaimer Statement | 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. |
| Brand IP Statement(s) re: (c), (TM), (SM) | Copyright SOURCE NATURALS, INC. |
| FDA Statement of Identity | Dietary Supplement |
| Physical state | Capsule |
| Registry snapshot | 2026-08-10 |
Source · NIH DSLD 274903 · label 2022-09-22; 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.