Before a company runs an ad, it has to have a "reasonable basis" for the claims. A "reasonable basis" means objective evidence that supports the claim. The kind of evidence depends on the claim. At a minimum, an advertiser must have the level of evidence that it says that it has. For example, the statement "Two out of three doctors recommend ABC Pain Reliever" which should be supported by a reliable survey to that effect.

If the ad is not specific, the FTC looks at several factors to determine what level of proof is necessary; including what experts in the field think is needed to support the claim. In most cases, ads that make health or safety claims must be supported by "competent and reliable scientific evidence" -- tests, studies, or other scientific evidence that has been evaluated by people qualified to review it. In addition, any tests or studies must be conducted using methods those experts in the field accept as accurate.