Finally, and aside from the USPSTF's findings, one must ask whether treating without first testing is sound practice. Certainly, it would be rational to do so if the condition being treated is prevalent and the treatment is safe and inexpensive. That is the case with another micronutrient, iodine, and the iodination of salt. However, the current situation is different because consuming sufficient iodine generally does not require conscious adherence to a particular regimen, whereas taking vitamin D does. Usually, testing improves patient adherence because it provides patient-specific, personally applicable information. General assurances that one probably needs extra vitamin D are not as compelling a motivator as knowing one's number. Thus, whether the practitioner adheres to the widely divergent guidelines of the IOM (4), the Endocrine Society (9), or the American Geriatrics Society (10), measuring vitamin D status seems to be warranted, not so much to diagnose deficiency but to determine patient status relative to the selected guideline.