Background: Visually estimated blood loss has long been known to be im-precise, inaccurate, and often underestimated, which may lead to delayed di-agnosis and treatment. Aim: To determine the accuracy of blood estimates by health workers in surgical and obstetric specialties. Methodology: This was a cross sectional single blinded observational study done in January 2016 to determine discrepancy between actual blood loss (ABL) and estimated blood loss (EBL) by consenting healthcare practitioners working in various surgical and obstetric departments of the Federal Medical centre, Owerri. Reconsti-tuted whole blood was obtained from the blood bank, and simulated scena-rios with known measured blood loss were created using common surgical materials. Visually estimated blood loss was performed by medical personnel. Percent errors of estimated blood loss were calculated and comparisons were made among the health professionals. The statistical analysis was done using SPSS version 21. Results: A total of 113 health professionals comprising 64 doctors and 49 nurses assessed 7 clinical scenarios. On the average, there was a general tendency for the health workers to under estimate the volume. Ma-jority of the participants underestimated the blood volume by more than 20% of actual volume. Though the nurses were more likely to underestimate blood volume than the doctors however, there was no statistical difference between the estimations by the nurses and the doctors except in station 3 with a p val-ue of 0.045. Conclusion: This finding calls for action in training and retrain-ing of every health worker in blood loss estimation, so that intervention can be initiated early.