Best Vitamins & Supplements Guide 2026

Sixty free calculators and more than a thousand guides. Every number traces back to a source you can open.

1,000+ guides · 60 free calculators · every claim names its source

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Vitamin D: mcg to IU Turn the microgram figure on the label into international units, or back again. mcg to IU, any nutrient Vitamins A, D and E each use a different conversion factor. This one handles all three. Magnesium dose by form Glycinate, citrate and oxide deliver very different amounts of elemental magnesium. Iron dose by form Ferrous, ferric and heme iron are not interchangeable. Work out the elemental dose. Vitamin D daily dose What to take, based on body weight and where you are starting from. Zinc dose by form Picolinate, citrate and gluconate compared on elemental zinc per capsule. B12 dose by form Methyl, cyano, hydroxo and adenosyl B12 are not absorbed the same way. Warfarin and vitamin K Steady intake matters more than low intake. Work out a daily target you can hold.

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Supplements, every guide 460 Reviews and comparisons 179 Drug and supplement interactions 146 Best for a condition 138 Peptides 120 Vitamins 93 Minerals and electrolytes 81

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Sources named, or it does not go up

We open every study we cite and check that it says what the article claims. Dosage figures are checked against the source, label data against the manufacturer, and anything reading as a medical claim gets cut. Where the evidence is thin, we say so instead of padding it.

The full method is public: How We Review Supplements. The people behind each subject area: Our Authors.

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