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SupplementAbsorption.comPreview · grades pending reviewer sign-off

Absorption, measured

How well is your supplement actually absorbed?

Blood levels and absorption rates from published studies, compared form by form. Every number is copied from a cited paper and labeled by species, so you can see what was measured in people and what wasn't.

Supplements
11
Full-text studies with data
782
Numbers invented
0

Supplements

  • Vitamin D

    Cholecalciferol (D3) is the best-characterized form: 13 human studies (total n=269) with measured absorption values (absorption evidence grade A, draft).

    Best evidence grade Grade AA: well characterized in people. Forms: 5+ human studies, 100+ participants, randomized/crossover designs, consistent values. Comparisons: agreeing head-to-head and matched single-form evidence with clear separation. All grades are drafts pending reviewer sign-off.204 studies · 136 human, 1 primate, 4 pig, 13 rodent, 40 other animal, 2 in vitro, 8 species unclear
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  • Magnesium

    Citrate measured higher than glycinate / bisglycinate in 1 human head-to-head study we have (grade B, draft).

    Best evidence grade Grade BB: solid human data. Forms: 3+ human studies. Comparisons: one randomized head-to-head, or matched single-form evidence from 2+ studies per form. All grades are drafts pending reviewer sign-off.171 studies · 85 human, 3 pig, 48 rodent, 32 other animal, 3 species unclear
    Read Magnesium →

  • Omega-3 / Fish Oil

    Ethyl ester is the best-characterized form: 12 human studies (total n=154) with measured absorption values (absorption evidence grade A, draft).

    Best evidence grade Grade AA: well characterized in people. Forms: 5+ human studies, 100+ participants, randomized/crossover designs, consistent values. Comparisons: agreeing head-to-head and matched single-form evidence with clear separation. All grades are drafts pending reviewer sign-off.164 studies · 102 human, 1 primate, 6 pig, 23 rodent, 24 other animal, 1 in vitro, 7 species unclear
    Read Omega-3 / Fish Oil →

  • Vitamin B12

    Cyanocobalamin is the best-characterized form: 7 human studies (total n=149) with measured absorption values (absorption evidence grade A, draft).

    Best evidence grade Grade AA: well characterized in people. Forms: 5+ human studies, 100+ participants, randomized/crossover designs, consistent values. Comparisons: agreeing head-to-head and matched single-form evidence with clear separation. All grades are drafts pending reviewer sign-off.134 studies · 82 human, 1 primate, 5 pig, 10 rodent, 23 other animal, 1 in vitro, 12 species unclear
    Read Vitamin B12 →

  • Coenzyme Q10

    Ubiquinol measured higher than ubiquinone in 1 human head-to-head study we have (grade B, draft).

    Best evidence grade Grade BB: solid human data. Forms: 3+ human studies. Comparisons: one randomized head-to-head, or matched single-form evidence from 2+ studies per form. All grades are drafts pending reviewer sign-off.114 studies · 59 human, 3 pig, 4 rodent, 36 other animal, 2 in vitro, 10 species unclear
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  • Curcumin (Turmeric)

    Curcumin + piperine is the best-characterized form: 3 human studies (total n=32) with measured absorption values (absorption evidence grade B, draft).

    Best evidence grade Grade BB: solid human data. Forms: 3+ human studies. Comparisons: one randomized head-to-head, or matched single-form evidence from 2+ studies per form. All grades are drafts pending reviewer sign-off.186 studies · 102 human, 17 rodent, 67 other animal
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  • Zinc

    Sulfate is the best-characterized form: 9 human studies (total n=103) with measured absorption values (absorption evidence grade A, draft).

    Best evidence grade Grade AA: well characterized in people. Forms: 5+ human studies, 100+ participants, randomized/crossover designs, consistent values. Comparisons: agreeing head-to-head and matched single-form evidence with clear separation. All grades are drafts pending reviewer sign-off.192 studies · 181 human, 1 primate, 10 pig
    Read Zinc →

  • Calcium

    Carbonate is the best-characterized form: 16 human studies (total n=369) with measured absorption values (absorption evidence grade A, draft).

    Best evidence grade Grade AA: well characterized in people. Forms: 5+ human studies, 100+ participants, randomized/crossover designs, consistent values. Comparisons: agreeing head-to-head and matched single-form evidence with clear separation. All grades are drafts pending reviewer sign-off.186 studies · 183 human, 1 rodent, 2 other animal
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  • Iron

    Ferrous sulfate is the best-characterized form: 40 human studies (total n=907) with measured absorption values (absorption evidence grade A, draft).

    Best evidence grade Grade AA: well characterized in people. Forms: 5+ human studies, 100+ participants, randomized/crossover designs, consistent values. Comparisons: agreeing head-to-head and matched single-form evidence with clear separation. All grades are drafts pending reviewer sign-off.222 studies · 222 human
    Read Iron →

  • Creatine

    Monohydrate is the best-characterized form: 3 human studies (total n=17) with measured absorption values (absorption evidence grade B, draft).

    Best evidence grade Grade BB: solid human data. Forms: 3+ human studies. Comparisons: one randomized head-to-head, or matched single-form evidence from 2+ studies per form. All grades are drafts pending reviewer sign-off.68 studies · 35 human, 15 rodent, 15 other animal, 3 species unclear
    Read Creatine →

  • CBD & CBDA (from hemp)

    Oil / full- or broad-spectrum is the best-characterized form: 7 human studies (total n=75) with measured absorption values (absorption evidence grade B, draft).

    Best evidence grade Grade BB: solid human data. Forms: 3+ human studies. Comparisons: one randomized head-to-head, or matched single-form evidence from 2+ studies per form. All grades are drafts pending reviewer sign-off.193 studies · 75 human, 2 primate, 4 pig, 18 rodent, 86 other animal, 3 in vitro, 5 species unclear
    Read CBD & CBDA (from hemp) →

How we grade

  • Grade AA: well characterized in people. Forms: 5+ human studies, 100+ participants, randomized/crossover designs, consistent values. Comparisons: agreeing head-to-head and matched single-form evidence with clear separation. All grades are drafts pending reviewer sign-off.Well characterized in people: 5+ human studies (100+ participants, randomized/crossover designs) with consistent values, or a form comparison backed by agreeing head-to-head and matched single-form studies.
  • Grade BB: solid human data. Forms: 3+ human studies. Comparisons: one randomized head-to-head, or matched single-form evidence from 2+ studies per form. All grades are drafts pending reviewer sign-off.Solid human data: 3+ studies, or one randomized head-to-head.
  • Grade CC: limited or conflicting human data: 1–2 studies, head-to-head and single-form evidence disagree, or baseline correction not reported. All grades are drafts pending reviewer sign-off.Limited or conflicting human data (1–2 studies, disagreement, or baseline correction not reported).
  • Grade DD: animal or lab data only, or conflicting comparisons. All grades are drafts pending reviewer sign-off.Animal or lab data only.

All grades are drafts pending sign-off by our reviewer, Dr. Colin Reily, PhD. Full methodology

Free API & AI-ready data

Every page is also available as JSON, with citations (PMID/DOI) and species labels on every value. AI assistants can read our llms.txt.

Please cite the original study and link the page section. Not medical advice.