Simple, fast and sensitive spectrophotometric method was developed for the determination of metformin in pharmaceutical formulations. The spectrophotometric procedure was based on the oxidation of metformin with potassium permanganate in alkaline medium. The developed method was also validated according to International Conference on Harmonization guidelines parameters like linearity, accuracy, precision, limit of detection and quantitation. Studies were conducted to investigate different parameters involved in color developments and optimized. The pure drug of metformin was extracted from pharmaceutical dosage form. Extraction procedure was developed, and possible reaction mechanism proposed in the manuscript. The IR spectrum of the extracted metformin was taken and compared with the simulated IR spectrum obtained from the density functional theory calculation. The vibrational assignment of the modes was done based on potential energy distribution.