Supplement guides
How to read a supplement offer before you buy
Plain-English guides on labels, doses, real prices, free trials and refunds. Written to help you check a product, not to sell you one.
Guides on this page
Vitamin K2 MK-7 doses and the blood thinner question
What MK-7 doses look like on labels versus in trials, and why people on blood thinners should ask before taking vitamin K2.
DosesHow much vitamin C is too much in a supplement?
Adults need 75 to 90 mg of vitamin C a day and the upper limit is 2,000 mg. Here is how real labels compare and how stacking adds up.
LabelsHow do I convert vitamin E IU to mg on a label?
Natural vitamin E is about 1.5 IU per mg. See the 15 mg RDA, the 1,000 mg limit and how real supplement labels print vitamin E.
SafetyWhat does a high-dose niacin label mean and why does it flush?
Niacin above 35 mg can flush the skin, niacinamide rarely does. See what real labels show and how to read the niacin line.
LabelsIs methylfolate better than folic acid on a supplement label?
Methylfolate vs folic acid: what mcg DFE means, the 400 mcg Daily Value, the 1,000 mcg upper limit and what the one head-to-head trial showed.
SafetyCan too much vitamin B6 in a supplement be harmful?
Vitamin B6 upper limit is 100 mg in the US and 25 mg in Europe. See nerve warnings, pyridoxine vs P5P and how to add up B6 across your labels.
DosesHow much selenium is safe in a supplement?
Selenium RDA is 55 mcg and the adult upper limit is 400 mcg. See the SELECT trial result, selenosis signs and how real labels hide the dose.
SafetyIodine and kelp in supplements: how much is too much?
Why supplements add iodine or kelp, the 150 mcg need and 1,100 mcg limit, and what to check on the label before buying.
DosesCalcium carbonate vs citrate: how much calcium is on the label?
Carbonate is 40% calcium, citrate 21%. How to read a calcium line, what the limits are and when the form matters.
LabelsRetinol or beta-carotene: what does vitamin A on a label mean?
Retinol, beta-carotene and mcg RAE explained: the daily value, the upper limit and what AREDS2 found about eye formulas.
Guides are general information, not medical advice. Read how we review and our medical disclaimer.