Electromagnetic interference (EMI) is a phenomenon that may occur when an electronic device is exposed to an electromagnetic (EM) field. The aim of this study was to investigate whether the CC could be interfered by exposure to the 900MHz cell phones in the laboratory. In addition, a review of the recent patents in electromagnetic interference is also presented. Human whole blood samples were collected from 20 healthy donors and each sample was divided to four aliquots and was placed into four batches for in vitro quantitative determination of human whole blood components. During CC reading of the first, second and third batches, the CC (Technicon H3 RTCTM, Bayer Diagnostics GmbH, München, Germany) was exposed to 1.90, 0.69 and 0.38 W/kg exposure of 900MHz radiation, respectively. For the fourth batch (control group), no radiation was applied. The final scores in the exposed batches I, II and III were statistically significant relative to the control batch (P = 0.03). The EMI caused profound changes on the CC reading of whole blood valid and macro cells in the exposed batches compared to the control batch (P = 0.001). This study showed that CC can be interfered by mobile phone RF radiation at a closed contact (less than 5cm distance). More accurate follow-up studies are needed for the evaluation of the electromagnetic interference due to radiofrequency radiation from external sources such as mobile phones in medical environments.