CEST imaging technique and MR scanning are used as an MRI method for detecting levels of lactate in vivo by exploiting the exchange of —OH protons on lactate with bulk water. In accordance with this method, one first obtains a lactate CEST MRI map of a slice of the body of a patient. A contrast agent such as pyruvate, glucose or glutamine is administered and a post-administration CEST MRI map is obtained. The difference in the spatial maps indicates the level of expression of lactate in the tissue of interest.