Background: Trace metals/metalloids were important for the biological functions of both the eukaryotic host and the microorganism. Their concentrations and variations may associate with the critical illness in sepsis, which still needs to be investigated. Methods: We performed a prospective cohort study on the patients with sepsis admitted to Tongji hospital (Wuhan, China) from Jul 01 to Dec 31, 2021. Sepsis was diagnosed in accordance with the third international consensus definitions for sepsis and septic shock (Sepsis-3). The concentrations of metals/metalloids including magnesium (Mg), calcium (Ca), chromium (Cr), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), mercury (Hg), thallium (Tl) and lead (Pb) in whole blood were analyzed by ICP-MS based methods. Results: Compared to the healthy controls, patients with sepsis showed higher levels of Ca, Cr and Cu, and lower levels of Mg, Mn, Fe, Zn, As, Hg and Pb. Further analysis between the critical illness and noncritical illness, revealed the Mn, Fe were significantly lower in the critically-ill sepsis. The longitudinal profile of the two metals show the differences appeared to exist almost throughout the clinical course. By performing the binary regression logistic analysis, we determined the Fe, Mn as independently risk factors for critical illness in sepsis, with effect sizes (beta) of 17.14 (95%CI: 1.79-163.81) and 10.83 (1.96-59.83), respectively, which collectively discriminated 83.3% of all cases between critical-illness and non-critically illness. Conclusions: The variations of whole blood metals/metalloids were associated with the critically-ill sepsis.