Vitamins
The vitamins panel reports population percentiles for vitamin and B12-pathway measures in NHANES: 25-hydroxyvitamin D, vitamin A (retinol), vitamin E (alpha-tocopherol), vitamin C, serum folate, red blood cell folate, vitamin B12, and methylmalonic acid. Reference values describe where a measurement sits in the US adult distribution; clinical reference intervals answer a different question.
Also listed under Nutrition .
Frequently Asked Questions
Why do different vitamins use different NHANES cycles?
Vitamin D, A, E, and C have no combined 2017-March 2020 pre-pandemic file released by NHANES, so they use the 2017-2018 single cycle with the cycle's MEC two-year weight. Serum folate and RBC folate have combined pre-pandemic files and use the folate subsample weight WTFOLPRP. Vitamin B12 and methylmalonic acid use NHANES 2013-2014. Each analyte page states its source cycle and weight.
Why are these population percentiles, not clinical reference intervals?
LabNorms shows where a given value sits in the US adult population distribution. Clinical reference intervals are produced by laboratories using their own measurement protocols and inclusion criteria, and answer a different question. Both can be useful, but they are not interchangeable.