WebMD

Effectiveness Levels

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The Effectiveness ratings are EVIDENCE-BASED. The FDA doesn't regulate herbs and dietary supplements like prescription drugs. Herbs and dietary supplements can be sold without ANY proof of effectiveness or safety. All medical literature is evaluated to determine Effectiveness ratings based on the best scientific evidence.

Each product is rated for a particular use or condition. If a product is used to treat more than one condition, you may find different effectiveness ratings for each use.

EFFECTIVE:
This product has passed a rigorous scientific review (similar to and as rigorous as the review of drugs done by the FDA)... and found to be effective for a specific use.

LIKELY EFFECTIVE:
Reputable scientific references generally agree that the product is effective for a specific use ... and at least two scientifically rigorous studies (involving at least several hundred patients) found the product to be likely effective... and the studies are published in reputable scientific journals.

POSSIBLY EFFECTIVE:
Reputable scientific references suggest that the product might work for a specific use ... and at least one study (in humans) found that the product might be effective.

POSSIBLY INEFFECTIVE:
Reputable scientific references suggest that the product might not work for a specific use... and at least one study (in humans) found that the product might not be effective.

LIKELY INEFFECTIVE:
Reputable scientific references generally agree that the product is not effective for a specific use... and at least two scientifically rigorous studies found the product likely to be ineffective... and the studies are published in reputable scientific journals.

INEFFECTIVE:
Most reputable scientific references agree that the product is not effective for a specific use... and no reliable human studies show the product to be effective.

INSUFFICIENT EVIDENCE:
If we know claims are being made about a product but there is no scientific info available about the effectiveness or ineffectiveness of the product, we'll let you know.