Store-brand vitamins and supplements can save you money, but they may not be as perfect a match to national brands as you often are led to believe. Examples…

Walgreens One Daily Women’s 50+ Multivitamin (about $13) may seem like a good substitute for Centrum Silver Women 50+ Multivitamin/Multimineral Supplement (about $16). But the Walgreens supplement contains only 23 specific vitamins, minerals and nutrients, while Centrum has 31, including boron and potassium, which are not in the Walgreens version, and higher daily doses of vitamins A, C and E. Which is better? That may depend on an individual shopper’s nutritional needs. But what’s clear is that the Walgreens version isn’t an exact substitute for the national brand.

CVS Advanced Eye Health softgel tablets (about $17) say on the label that they’re “comparable” to the AREDS 2 study formula softgels popularized by Bausch & Lomb PreserVision (about $35). The Bausch & Lomb product contains all six ingredients that were used in that study by the National Institutes of Health, which resulted in slower progression of age-related macular degeneration, a very serious eye condition that could lead to partial blindness. The CVS product contains only two of the six ingredients—lutein and zeaxanthin—while leaving out all of the study’s proven vitamins and minerals (vitamin C, vitamin E, copper and zinc).

Bottom line: Compare ingredients carefully.