Serving size and actual amount
One serving may be one capsule, multiple tablets or a scoop. Multiply ingredient amounts by the number of servings you intend to take. Compare active ingredients rather than bottle size or the number of marketing claims.
A familiar ingredient name does not tell you its dose or form. Magnesium glycinate, for example, is commonly described by compound weight and elemental magnesium amount; those figures are not interchangeable.
Quality signals
Check manufacturer identity, lot number, expiration date, allergen statements, storage instructions and any reputable third-party testing information that is actually documented. Do not treat an attractive seal or vague ‘lab tested’ slogan as proof of a particular certification.
Interactions and exceptions
Supplements can interact with medications or be inappropriate for some conditions. Ask a pharmacist or clinician when uncertain, especially before combining multiple products with overlapping ingredients.
Further reading
FDA: unapproved GLP-1 medicines
NIH: understanding dietary supplements