Objective: Lithium was recently proclaimed to be an essential trace element in human nutrition . The aim of this study was to assess lithium nutritional status by analyzing lithium frequency distribution in the long-term biological indicator tissue of hair (H-Li) and in the short-term biological indicator tissue of whole blood (WB-Li). Materials and methods: Hair samples were analyzed in 1,073 apparently healthy adult Croats (339 males and 734 females) and the whole-blood lithium was analyzed in a random subsample of them (91 males and 143 females). Samples were analyzed using ICP-MS at the Center for Biotic Medicine, Moscow, Russia. Results: There were no gender-dependent differences in the lithium-adequate linear reference range for H-Li and WB-Li where lithium was (mu g x g(-1)) 0.014 - 0.100 and 3.40 - 5.65, respectively. Conclusion: Lithium concentrations below 0.014 mu g x g(-1) for H-Li and 3.40 mu g x g(-1) for WB-Li would indicate lithium deficiency. The estimated upper safety lithium limits for H-Li and WB-Li were set at 0.100 and 6.65 mu g x g(-1), respectively. These preliminary data are important for a long-term biomonitoring of low-level lithium supplementation.