{
  "name": "Gentle Iron: Form, Dose and Schedule Census with Cost per 25 mg",
  "license": "https://creativecommons.org/licenses/by/4.0/",
  "attribution": "Verified Supplement Data, https://verifiedsupplementdata.com/iron/non-constipating/",
  "dateModified": "2026-09-21",
  "methodology": "Three reads of the NIH Dietary Supplement Label Database: iron labels (form, directed schedule, dose tier), labels whose iron row names a bisglycinate/Ferrochel/chelate form, and liquid iron labels. Every figure recomputed in two halves; figures that did not agree within 8 points (shares) or 25% (medians) are not published.",
  "ironLabelCensus": {
    "source": "NIH Dietary Supplement Label Database (DSLD) v9",
    "sourceUrl": "https://dsld.od.nih.gov/",
    "retrievedOn": "2026-08-29",
    "labelsRetrieved": 2004,
    "labelsWithIronRow": 1592,
    "labelsWithDirection": 1961,
    "brands": 459,
    "rdaMg": {
      "menAndPostmenopausalWomen": 8,
      "menstruatingWomen": 18
    },
    "upperLimitMg": 45,
    "labelsDirectingDaily": 1961,
    "labelsDirectingAlternateDay": 0,
    "labelsAtOrBelowRda": 1090,
    "atOrBelowRdaPct": 68.5,
    "medianDirectedDailyMg": 18,
    "doseByForm": {
      "bisglycinateOrChelate": {
        "form": "Bisglycinate / chelate",
        "labels": 417,
        "median": 18,
        "p90": 29
      },
      "ferrousSulfate": {
        "form": "Ferrous sulfate",
        "labels": 108,
        "median": 28,
        "p90": 65
      },
      "note": "held: \"the gentle form is dosed below ferrous sulfate\""
    },
    "validation": {
      "method": "split-half by DSLD read order",
      "checked": 8,
      "held": 5,
      "failed": [
        "most labels as directed exceed the UL",
        "most of the market sells above the typical dose",
        "a large share sells above the studied range"
      ]
    },
    "notPublished": [
      "most labels as directed exceed the UL",
      "most of the market sells above the typical dose",
      "a large share sells above the studied range",
      "per-serving median (unstable between halves)",
      "share above the UL per serving (unstable between halves)"
    ]
  },
  "bisglycinateCensus": {
    "retrievedOn": "2026-08-29",
    "labelsRetrieved": 1587,
    "labelsSoldAsIron": 560,
    "labelsAnalysed": 168,
    "pureBisglycinateLabels": 145,
    "brands": 96,
    "medianElementalMgPerServing": 25,
    "p25MgPerServing": 15,
    "p75MgPerServing": 28,
    "medianElementalMgPerUnit": 25,
    "medianDirectedDailyMg": 25,
    "atLeast18MgPerServingPct": 73.8,
    "directsOver45MgDailyPct": 3.6,
    "blendsAnotherIronFormPct": 13.7,
    "namedGentlePct": 5.4,
    "capsuleOrTabletPct": 85.7,
    "twoPlusUnitsPerServingPct": 26.2,
    "validation": {
      "method": "split-half by DSLD label-id parity; shares within 8 points, medians within 25%",
      "checked": 12,
      "held": 11,
      "failed": [
        "share at most 25 mg per serving"
      ]
    },
    "notPublished": [
      "share at most 25 mg per serving"
    ]
  },
  "liquidIronCensus": {
    "retrievedOn": "2026-09-15",
    "labelsRetrieved": 166,
    "labelsSoldAsIron": 63,
    "brands": 46,
    "medianElementalMgPerServing": 10,
    "p75DailyMg": 20,
    "atLeast45MgDailyPct": 1.7,
    "formDeclaredPct": 77.8,
    "bisglycinateShareOfDeclaredPct": 24.5,
    "polysaccharideIronShareOfDeclaredPct": 10.2,
    "ferricShareOfDeclaredPct": 20.4,
    "childTargetedPct": 58.7,
    "validation": {
      "method": "split-half by DSLD label-id parity (the harvest pooled two populations - an earlier shelf read and a format search - so read order is not a random split)",
      "checked": 17,
      "held": 9,
      "failed": [
        "median daily elemental iron mg",
        "p25 daily mg",
        "share at least 18 mg/day",
        "share at most 10 mg/day",
        "ferrous sulfate share of declared",
        "ferrous gluconate share of declared",
        "median daily mg, adult",
        "vitamin C co-formulated share"
      ]
    },
    "notPublished": [
      "median daily elemental iron mg",
      "p25 daily mg",
      "share at least 18 mg/day",
      "share at most 10 mg/day",
      "ferrous sulfate share of declared",
      "ferrous gluconate share of declared",
      "median daily mg, adult",
      "vitamin C co-formulated share"
    ]
  },
  "trialBasis": {
    "ferrousSulfateGiOddsRatioVsPlacebo": {
      "value": 2.32,
      "trials": 43,
      "participants": 6831,
      "source": "Tolkien 2015, PMID 25700159"
    },
    "bisglycinateGiIncidenceRateRatioPregnancy": {
      "value": 0.36,
      "trials": 17,
      "source": "Fischer 2023, PMID 36728680"
    },
    "alternateDayGiSideEffectRatio": {
      "dailyVsAlternate": 1.56,
      "participants": 150,
      "doseMg": 100,
      "source": "von Siebenthal 2023, PMID 38021373"
    },
    "alternateDayAbsorption": {
      "consecutivePct": 16.3,
      "alternatePct": 21.8,
      "doseMg": 60,
      "participants": 40,
      "source": "Stoffel 2017, PMID 29032957"
    }
  },
  "costPer25Mg": [
    {
      "name": "NOW Foods Iron 36 mg Double Strength (Ferrochel)",
      "brand": "NOW Foods",
      "slug": "now-iron-36-ferrochel",
      "form": "iron bisglycinate (chelate)",
      "liquid": false,
      "elementalMgPerServing": 36,
      "elementalMgPerUnit": 36,
      "servingSize": "1 capsule",
      "servingsPerContainer": 90,
      "priceUsd": 9.57,
      "priceVerifiedOn": "2026-09-20",
      "costPer25MgUsd": 0.074,
      "unitsFor25Mg": 0.7,
      "certification": "None",
      "nihDsldId": null,
      "availability": "ok",
      "infantProductNotRanked": false
    },
    {
      "name": "Thorne Iron Bisglycinate 25 mg",
      "brand": "Thorne",
      "slug": "thorne-iron-bisglycinate-25",
      "form": "iron bisglycinate (chelate)",
      "liquid": false,
      "elementalMgPerServing": 25,
      "elementalMgPerUnit": 25,
      "servingSize": "1 capsule",
      "servingsPerContainer": 60,
      "priceUsd": 16,
      "priceVerifiedOn": "2026-09-20",
      "costPer25MgUsd": 0.267,
      "unitsFor25Mg": 1,
      "certification": "NSF Certified for Sport",
      "nihDsldId": null,
      "availability": "ok",
      "infantProductNotRanked": false
    },
    {
      "name": "MegaFood Blood Builder",
      "brand": "MegaFood",
      "slug": "megafood-blood-builder",
      "form": "iron bisglycinate (chelate)",
      "liquid": false,
      "elementalMgPerServing": 26,
      "elementalMgPerUnit": 26,
      "servingSize": "1 tablet",
      "servingsPerContainer": 90,
      "priceUsd": 28.99,
      "priceVerifiedOn": "2026-09-20",
      "costPer25MgUsd": 0.31,
      "unitsFor25Mg": 1,
      "certification": "NSF Certified",
      "nihDsldId": null,
      "availability": "ok",
      "infantProductNotRanked": false
    },
    {
      "name": "Enfamil Fer-In-Sol Iron Drops (50 mL)",
      "brand": "Enfamil",
      "slug": "enfamil-fer-in-sol-drops",
      "form": "ferrous sulfate, drops",
      "liquid": true,
      "elementalMgPerServing": 15,
      "elementalMgPerUnit": 15,
      "servingSize": "1 mL dropper",
      "servingsPerContainer": 50,
      "priceUsd": 10.49,
      "priceVerifiedOn": "2026-09-20",
      "costPer25MgUsd": 0.35,
      "unitsFor25Mg": 1.7,
      "certification": "None stated",
      "nihDsldId": "208588",
      "availability": "ok",
      "infantProductNotRanked": true
    },
    {
      "name": "Nature's Way Liquid Iron 18 mg (16 fl oz)",
      "brand": "Nature's Way",
      "slug": "natures-way-liquid-iron-18",
      "form": "ferric glycinate, liquid",
      "liquid": true,
      "elementalMgPerServing": 18,
      "elementalMgPerUnit": 18,
      "servingSize": "1 tablespoon (15 mL)",
      "servingsPerContainer": 32,
      "priceUsd": 9.1,
      "priceVerifiedOn": "2026-09-20",
      "costPer25MgUsd": 0.395,
      "unitsFor25Mg": 1.4,
      "certification": "None stated",
      "nihDsldId": "333921",
      "availability": "ok",
      "infantProductNotRanked": false
    },
    {
      "name": "MegaFood Blood Builder Liquid Iron (7.7 fl oz)",
      "brand": "MegaFood",
      "slug": "megafood-blood-builder-liquid-iron",
      "form": "iron bisglycinate, liquid",
      "liquid": true,
      "elementalMgPerServing": 8,
      "elementalMgPerUnit": 8,
      "servingSize": "1/2 teaspoon (3 mL); label allows up to 10 mL",
      "servingsPerContainer": 76,
      "priceUsd": 24.99,
      "priceVerifiedOn": "2026-09-20",
      "costPer25MgUsd": 1.028,
      "unitsFor25Mg": 3.1,
      "certification": "None stated",
      "nihDsldId": "333193",
      "availability": "ok",
      "infantProductNotRanked": false
    },
    {
      "name": "Floradix Iron + Herbs (17 fl oz)",
      "brand": "Floradix",
      "slug": "floradix-iron-herbs-17oz",
      "form": "ferrous gluconate, liquid",
      "liquid": true,
      "elementalMgPerServing": 10,
      "elementalMgPerUnit": 10,
      "servingSize": "10 mL (label directs twice daily)",
      "servingsPerContainer": 50,
      "priceUsd": 30.59,
      "priceVerifiedOn": "2026-09-20",
      "costPer25MgUsd": 1.529,
      "unitsFor25Mg": 2.5,
      "certification": "None stated",
      "nihDsldId": "276594",
      "availability": "ok",
      "infantProductNotRanked": false
    },
    {
      "name": "Pure Encapsulations Iron Liquid (4.1 fl oz)",
      "brand": "Pure Encapsulations",
      "slug": "pure-encapsulations-iron-liquid",
      "form": "ferric pyrophosphate, liquid",
      "liquid": true,
      "elementalMgPerServing": 15,
      "elementalMgPerUnit": 15,
      "servingSize": "1 teaspoon (5 mL)",
      "servingsPerContainer": 24,
      "priceUsd": 38.5,
      "priceVerifiedOn": "2026-09-20",
      "costPer25MgUsd": 2.674,
      "unitsFor25Mg": 1.7,
      "certification": "None stated",
      "nihDsldId": "302461",
      "availability": "ok",
      "infantProductNotRanked": false
    }
  ]
}