Supplement Buying Guides
Every supplement we cover is scored on the same 6-metric rubric — so you can see exactly why one magnesium, probiotic, or multivitamin ranks ahead of another. Read the scoring methodology →
Best Magnesium Supplements, Scored on a Public Rubric
We scored 7 top-selling Amazon magnesium supplements on a public 6-metric rubric — third-party testing, form, value, transparency, and more.
Best Probiotic Supplements, Scored on a Public Rubric
Side-by-side scoring of six probiotics on our 6-metric rubric: named strains, CFU dose, third-party testing, shelf-stability, and value.
Best Fish Oil Supplements, Scored on a Public Rubric
We scored six fish oil supplements on our 6-metric rubric: EPA/DHA dose, oxidation, third-party testing, and value per gram of omega-3.
Best Vitamin D Supplements, Scored on a Public Rubric
We scored six vitamin D3 supplements on our 6-metric rubric: dose accuracy, K2 pairing, third-party testing, and value per IU.
Best Collagen Peptides, Scored on a Public Rubric
Six top-selling collagen peptide supplements compared on our 6-metric rubric — molecular weight, source, third-party testing, and value.
Best Ashwagandha Supplements, Scored on a Public Rubric
Five ashwagandha supplements scored on our 6-metric rubric: extract type (KSM-66, Sensoril), withanolide content, and third-party testing.
Best Multivitamins, Scored on a Public Rubric
Six multivitamins compared on our 6-metric rubric: bioavailable forms (methylated folate, MK-7, methylcobalamin), third-party testing, and value.
Best Berberine Supplements, Scored on a Public Rubric
Berberine has real, modest evidence for blood sugar and cholesterol — and it is not "nature's Ozempic." Its biggest problem is absorption, not marketing. We scored seven widely-available options on a 6-metric rubric weighted toward the dose the trials used and the forms that survive first-pass metabolism.
Best Vitamin C Supplements, Scored on a Public Rubric
Your plasma saturates near 200 mg a day, and above 1 g absorption falls below 50% — so most of a mega-dose is urine. We scored seven vitamin C options on the dose that actually absorbs, not the number on the front of the bottle.
Best Zinc Supplements, Scored on a Public Rubric
The adult RDA is 11 mg. The upper limit is 40 mg. Most of the aisle sells 50 and 100 mg — and 50 mg for weeks quietly starves your copper. We scored seven zinc supplements on the dose that respects the ceiling, not the number on the front.
Best Iron Supplements, Scored on a Public Rubric
Iron is the one supplement you should not buy on a hunch — get the blood test first. Then take less, every other day: 60 mg on alternate days absorbed more total iron than the same dose taken daily. We scored seven iron supplements on dose, form, and tolerability.
Best CoQ10 Supplements, Scored on a Public Rubric
Ubiquinol is rarely the upgrade the label promises, and CoQ10 won't reliably fix statin muscle pain. We scored seven CoQ10 supplements on form, dose, third-party testing, and honest value.
Best Vitamin B12 Supplements, Scored on a Public Rubric
The methylcobalamin premium isn't earned and B12 won't give a non-deficient person energy. We scored seven B12 supplements on form-neutral value, third-party testing, and honest dosing.
Best Turmeric Supplements, Scored on a Public Rubric
Curcumin barely absorbs on its own, so the formulation is the whole game. We scored seven turmeric supplements on standardized curcuminoids, real absorption enhancers, testing, and honest claims.
Best Biotin Supplements, Scored on a Public Rubric
Biotin deficiency is rare and the aisle sells 10,000 mcg for a 30 mcg need. We scored seven biotin supplements on honest dosing, third-party testing, and the FDA lab-interference warning you need to know.
Best Glucosamine Supplements, Scored on the Evidence
The big trials are mixed and rheumatology guidelines now advise against it — but glucosamine is cheap and low-risk. We scored seven on form (sulfate over HCl), clean labels, and third-party testing.
The Best Greens Powders — and Why a Plate of Vegetables Still Wins
Greens powders don't replace vegetables, and most of the marketing is proprietary-blend fairy dust. We rank the ones with real greens, honest labels, and third-party testing — and say plainly where the money is wasted.
The Best Fiber Supplements — and Why Food Comes First
Psyllium has the best evidence — for regularity, cholesterol, and blood sugar. We rank fiber supplements by fiber type, tolerability, and value, and say plainly that whole food should come first.
The Best Calcium Supplements for Bone Health
Food is the best calcium source, and more isn't better. We rank calcium citrate and carbonate supplements, explain the absorption differences, and are honest about the 500 mg-per-dose limit and the vitamin D pairing.
The Best Tart Cherry Supplements for Recovery and Sleep
Tart cherry has modest but real evidence for muscle-recovery soreness and sleep quality. We rank concentrates and extracts, favor the studied Montmorency form, and keep the claims honest.
The Best Prebiotic Supplements for Gut Health
A prebiotic feeds the good bacteria you already have — it's not a probiotic and it's not magic. We rank inulin, GOS, resistant starch, and acacia picks on evidence, tolerability, and value, food-first throughout.
The Best Mushroom Supplements, Judged on What's Actually in the Bottle
Functional-mushroom supplements are one of the most oversold categories on the shelf. We rank lion's mane, cordyceps, reishi, and blends on the one number that matters — verified beta-glucans from a real fruiting body — with the evidence stated plainly.
The Best Nootropic Supplements, Ranked by What They Actually Disclose
Most 'brain supplements' hide their doses inside a proprietary blend. We rank nootropics on the one thing that predicts whether they'll work — every milligram disclosed — and name the best-evidenced option, which costs about six cents a day.
Best Joint Supplements, Ranked by How Good the Evidence Actually Is
The joint aisle is built on the one ingredient rheumatology now recommends against. We ranked seven joint supplements across five ingredient classes by how good the evidence actually is.