01 / Evidence-based supplement data

The price that matters is per clinical dose.

We compare supplements by the cost to take the amount actually studied in trials — every claim linked to its source, every label checked against the NIH database, no paid placement.

New here? Start with how to decide what you actually need before you compare a single product — including the specific short list of what most adults should (and shouldn't) take.

Look up any supplement label → Browse supplements A–Z

Strong evidence Moderate Limited we grade every claim, and say so plainly

Magnesium · how much of the pill is magnesium

Glycinate

gentle form, often chosen for tolerance

~14%

Citrate

common, low cost

~16%

Oxide

most magnesium per pill, poorly absorbed

~60%

Share of each form’s weight that is elemental magnesium. A bigger number on the label is not the same as more magnesium absorbed. Forms compared

Sourcing

Every claim → a PMID

Products

Checked vs NIH DSLD

Ranking

Cost / clinical dose

Independence

No paid placement

Every supplement, ranked by cost per dose.

Forms compared, evidence-graded, products named — pick a starting point.

MagnesiumMineral

8forms

Glycinate vs citrate vs oxide. Forms, dosing, and cost.

Browse →

Vitamin DVitamin

600 IUadult RDA

D2 vs D3, the 1000–5000 IU debate, K2 pairing, who needs what.

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IronMineral

2–3×absorption

Ferrous sulfate vs bisglycinate, tolerability, and cost.

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Omega-3Fatty acid

70%swing

EPA vs DHA, triglyceride vs ethyl ester, the best-value fish oil.

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AshwagandhaAdaptogen

20+RCTs

KSM-66 vs Sensoril vs generic. What the trials used.

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CreatinePerformance

500+studies

Monohydrate vs HCl, dosing, and cost.

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Browse all supplements A–Z →

Best picks.

Our newest buying guides. Each one names our pick and shows why.

Best Lion's Mane Supplements

Our 3 picks, plus how to buy a real one.

Best Vitamin K2 Supplements

Our 4 picks, plus MK-7 vs MK-4 and how much to take.

Best L-Theanine Supplements

Our 3 picks, plus the dose and how it pairs with caffeine.

Best Ashwagandha Supplements

Our 3 picks, plus what the trials measured.

Best Iron Supplements

Our 4 picks, plus which form is easier on your stomach.

Ghost Whey vs Optimum Nutrition

Which of the two to buy, side by side.

Full guides: Iron · Lion's mane · L-theanine · Vitamin K2 · Ashwagandha

Popular guides.

The questions people actually search — answered with the evidence.

What Supplements Should You Actually Take?

The four filters that narrow a shelf down to one or two products.

Best Magnesium Supplement

Magnesium forms compared by elemental dose, label directions and cost per day.

Vitamin D Dosage Guide

D2 vs D3, K2 pairing, and the label doses sold on the shelf.

Most-researched guides.

Deep buying guides — every pick ranked by cost per clinical dose.

Best Tongkat Ali Supplement

Ranked by eurycomanone standardization, studied dose, and cost.

Tongkat Ali Supplement Guide

Product data and specs for every listed brand.

Magnesium Dosage Guide

NIH intake ranges by age and sex — plus the upper limit.

Best Creatine Monohydrate

Ranked by cost per 5g dose and Creapure purity.

Best Fish Oil Supplement

Ranked by cost per 2000mg EPA+DHA, the clinical dose.

Best Collagen Supplement

Ranked by dose, peptide type, and cost per day.

Best Electrolyte Drinks

Ranked by real sodium per serving and third-party testing.

Ferrous Sulfate vs Bisglycinate

Which iron form is gentler on your stomach.

Original research.

Our own analysis of the product data — not a rehash of press releases.

The Supplement Price Spread

How much the same supplement can cost per day across brands and forms.

The Certification Gap

How many products carry zero third-party certification.

Free tools.

Run your own numbers — nothing leaves your browser.

Supplement Lookup

Search 207,000+ verified labels from the NIH DSLD.

When the evidence changes, you'll know.

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Medical disclaimer: Educational health information based on published clinical research — not medical advice, and not a replacement for your physician. Always discuss supplement changes with your doctor, especially if you take medications or have a health condition. Methodology.

Affiliate disclosure: As an Amazon Associate, we earn from qualifying purchases. Rankings are determined by cost per effective dose and clinical evidence, not affiliate commissions. Read our methodology.