To establish a blood lead quantification correlation from two occupational health laboratories (OHL1V and OHL2DF), and the ABC Hospital (LABC) metals laboratory. A cross-sectional study was performed in 84 workers from a voltage regulators company, where lead is welded; in 54 % (46 of them) a blood sample was taken and analyzed by OHL1V, and in 28.6 % (24) by OHL2DF. All samples were analyzed by atomic absorption spectrophotometry. Pearson correlation (r), coefficient of determination (r2), Lin (rho) concordance test, and Bland-Altman plots were calculated. The blood lead mean: LABC was 5.8 ± 2.4 μg/dL vs. OHL2DF of 4.4 ± 3.6 μg/dL (r = 0.25 [p = 0.24], r2 = 0.06 [p = 0.24], and rho = 0.21 [p = 0.21]). And with LABC, 6.75 ± 3.3 μg/dL vs. OHL1V 5.6 ± 2.9 μg/dL (r = 0.91 [p < 0.001], r2 = 0.83 [p < 0001], and rho = 0.85 [p< 0.001]). Agreement between LABC and OHL1V was poor (< 0.90), and with OHL2DF was null. An occupational health laboratory certification is needed in order to have reliable biological exposure index measurements in lead occupational exposure.