...the two groups do not agree if there are data to support defining additional vitamin D physiological states, e.g. insufficiency, sufficiency and toxicity based on 25(OH)D concentrations. ...those national recommendations conflict with a third set of recommendations from non-governmental medical societies and organisations(1), for example, the Endocrine Society, with no prospect for resolving the differences among the three approaches(1,2). In the last 10 years, enormous progress has been made in collecting nationally representative survey data that meet those requirements(11–16), but despite this progress, we remain woefully behind in generating the vitamin D research data necessary to break out of the paralysis. ...we have at a minimum three basic approaches for defining different states of vitamin D status, and no way to determine which is most appropriate. ...the Vitamin D External Quality Assessment Scheme (DEQAS) was introduced in 1989 to improve the reliability of 25(OH)D assays(26). Similar results were found in the recent analysis of data from the College of American Pathologists (CAP) Accuracy-Based Vitamin D (ABVD) survey(31). ...using a chromatography-based assay and participating in an external quality assessment programme does not assure that ‘25(OH)D’ results from research studies or national surveys are accurate(31,32).