Modern approach towards biodegradable biomaterials involves significant capability of magnesium (Mg) alloys. Being a major constituent of the human body, Mg has extraordinary potential to facilitate as temporary orthopaedic implants. Despite many benefits within Mg and its alloys; such as excellent biocompatibility, biodegradability, satisfactory mechanical qualities, its use is still very limited. Rapid corrosion and hydrogen evolution are threats to its limited use. To estimate the mechanism and causes of corrosion in living environments for Mg-alloys accurately, in vitro study is necessary. The present review focuses on factors influencing corrosion rates (bio-corrosion) of Mg-alloys in vivo and in vitro studies. To understand the corrosion behaviour, factors like organic compounds, inorganic ions and some experimental process parameters taken into considerations and are analyzed. It is concluded that some of these factors affect the mechanism of corrosion greatly and their effective management is required to control their corrosion rates. Experimental conditions are most significant because they affect corrosion rates the most and can be helpful to stabilize it. The effects of these factors are summarized at the end of this review.