Vitamin A status assessment is not straightforward. Retinol isotope dilution (RID) testing requires time for the tracer dose to mix with the total body stores of vitamin A (TBS). Researchers are interested in shortening the time interval between tracer administration and follow-up blood draws, and in re-examining current assumptions about liver mass for calculation of total liver vitamin A reserves (TLR, in m mol/g liver). Schoolchildren (aged 7–12 years; n ¼ 72) were recruited from one school in Burkina Faso. After a baseline blood draw, 1.0 m mol [14,15]- 13C 2 -retinyl acetate was administered to estimate TBS and TLR by retinol isotope dilution with follow-up blood samples at days 7 and 14. Correlations were determined to evaluate if sampling at day 7 could be used to predict TLR compared with day 14. Liver mass was estimated using body surface area and compared with the currently used assumption of liver weight equivalent to 3% of body weight. (This trial was registered at Pan African Clinical Trial Registry: PACTR201702001947398). Liver mass calculated using body surface area did not differ from the standard assumption of 3% of body weight and yielded similar TLR values. The children in this study had mean TLR (0.67  0.35 m mol/g) in the adequate range, while serum retinol concentrations (0.92  0.33 m mol/L) predicted 25% vitamin A deficiency. TLR values at seven days were highly correlated with, but significantly different from day 14 (P

Burkina Faso liver mass retinol enrichment stable isotope total body vitamin A stores