Products tested represent those commonly sold and/or available nationally in the U.S. and Canada. ConsumerLab.com purchased products on the open market through retail stores, on-line retailers, and direct sales or multi-level marketing companies. Products were not accepted directly from manufacturers.
Vitamin C products were tested in one or more independent laboratories for the following:
Ascorbic acid by High Performance Liquid Chromatography (HPLC) or capillary electrophoresis (CE);
Lead, arsenic, cadmium content by ICP-MS (inductively Coupled Plasma-Mass Spectroscopy); and
Non-chewable, non-capsule, non-enteric coated and non-time-release formulations were analyzed for disintegration utilizing USP (United States Pharmacopeia) <2040> recommendations entitled "Disintegration and Dissolution of Nutritional Supplements."
Any product not passing any initial testing criteria was sent to a second independent laboratory for repeat analysis using similar methodologies.
Identities of products were not disclosed to laboratories performing the testing.
Contain 100% and no more than 120% of claimed amount of ascorbic acid.
Not exceed the following limits for elemental lead: **
Products marketed for use by children may not exceed the State of California's Prop 65 limits for lead in dietary supplements of 0.5 mcg per recommended daily serving with an additional allowance of 0.8 mcg if the product contains more than 1,000 mg/day of calcium.
Products with a single serving weights of less than 5 grams which are not marketed for use by children, may not exceed the State of California's Prop 65 limits for lead in dietary supplements of 0.5 mcg per recommended daily serving with an additional allowance of 0.4 mcg if containing 250-999 mg/day of any combination of elemental calcium, magnesium and potassium or 0.8 mcg if containing more than 1,000 mg/day of any combination of these minerals. An additional allowance of 0.5 mcg is provided if containing 250-999 mg/day of whole herb (not extract) or 1.0 mcg if containing 1000 mg/day or more of whole herb (not extract). However, total lead allowance will not exceed 2 mcg.
Products with single serving weights of 5 grams or more which are not marketed for children may not exceed 2.5 mcg per serving or 4.0 mcg per daily serving.
Contain less than 10 micrograms of total arsenic and no more than 5 micrograms of inorganic arsenic per daily serving (EPA limit - based on 1 liter of water).
Contain less than 0.3 micrograms of cadmium per gram (World Health Organization/ADI proposed in dried plant materials).
If applicable to the product, it must meet recommended USP <2040> parameters of disintegration for dietary supplements (excluding capsule, enteric coated, chewable and time-release products).
Be in compliance with FDA labeling requirements.
A "Pass" was based on meeting the above criteria in either the first or second rounds of testing.
* Passing scores allow for specific margins of technical error associated with each analysis. ConsumerLab.com reserves the right to disqualify a product at any time from passing its testing if it considers such product to present a safety risk or to provide misleading or inaccurate information in its labeling.
** If available for sale in California, a product that exceeds the State of California's Prop 65 lead limit requires a warning label. However, with or without this warning label, a product cannot pass ConsumerLab.com testing if it exceeds the levels described in this paragraph.