How We Calculate Everything

Where the data comes from

Each compound record cites its own sources — the NIH Office of Dietary Supplements, Examine.com and indexed PubMed identifiers, linked directly on every page. Records carry an evidence level from A to C and a last-reviewed date.

Nothing is scraped from competitor sites, and no figure is invented to fill a gap. Where a value does not exist for a compound, the field is left empty rather than estimated.

Compatibility score

A pair starts at a neutral 70 — the baseline for any combination that has never been studied. From there the score moves only when the underlying records say it should:

• documented synergy: +12 at evidence level A, +8 at B, +5 at C
• documented antagonism: −30 for major clinical significance, −18 moderate, −9 minor
• both directions are checked — compound A may list B without B listing A
• the result is clamped to 5–99 and recalculated on every request, never stored

Elemental percentage

This is how much of a compound is the mineral itself, as opposed to the carrier the label counts as weight. It is calculated from the molecular formula and molecular weight: the atomic weight of the mineral, multiplied by the number of its atoms in the formula, divided by the molecular weight of the compound.

Worked example: magnesium glycinate is C4H8MgN2O4 at 172.42 g/mol, and magnesium weighs 24.305 — so 24.305 / 172.42 = 14.1% elemental magnesium. Magnesium oxide, by contrast, is 60.3% elemental magnesium, which is why it looks superior on a label.

Cost per 100 mg absorbed

The only honest way to compare price across forms. Monthly cost is divided by the amount that actually reaches the bloodstream, which means multiplying the daily dose by the elemental percentage and then by absorption.

This reverses the ranking you get from shelf price: magnesium oxide is the cheapest capsule and one of the most expensive ways to deliver magnesium, because only about 4% of it is absorbed.

The metric is skipped where it would be misleading — for compounds dosed in IU or CFU rather than milligrams.

Known limitations

We would rather state these than have you discover them:

• absorption is dose-dependent — fractional uptake falls from roughly 65% at low intakes to 11% at high ones, while our figures are single values per form
• absorption also varies with food, gut health, age and genetics, none of which is modelled
• the compatibility score covers supplement-to-supplement records only; medication interactions are listed separately and never folded into the number
• "no known interaction" means no documented evidence, not evidence of safety — most pairs have never been studied
• evidence level B or C means the effect is plausible, not established

What we deliberately do not do

• no star ratings or review counts — we have no reviewers, and inventing them is fraud
• no Product or Offer markup on information pages, and no aggregate ratings anywhere
• no pages generated for combinations nobody searches for
• no claims that a supplement treats, cures or prevents disease

Who maintains this

The database is compiled and maintained by Denis, the site owner. Every figure is either taken from a cited source or derived by a formula published on this page — nothing here rests on personal authority.

To be explicit about the limits: I hold no medical or nutritional qualification. I built this because the answers I wanted — which form actually absorbs, what a combination does, how much reaches the bloodstream — were scattered across product pages that had something to sell. So the site shows the arithmetic and the sources instead of asking you to trust me.

What that means in practice: use these numbers to compare options and to prepare questions for a clinician who can see your full picture. Do not use them as a treatment decision.

Open to review

If you are a physician, pharmacist, registered dietitian or researcher and willing to check a section, write in — you will be credited by name on every page you review, with the review date. That applies whether you confirm the data or tear it apart; a corrected figure is worth more than an unchallenged one.

Corrections

If a dosage, interaction or absorption figure looks wrong, tell us and point to the source — corrections to the database take priority over new features. Two values were corrected on 2026-07-30 after review: magnesium oxide absorption from 15% to 4%, and curcumin from 20% to 5%, both per systematic reviews of bioavailability. Each correction is recorded in the compound record with its reason and date.

Write to [email protected]. If you are a clinician or researcher willing to review a section, we will credit you on the pages you review.