Glucose taken up by cancer cells is thought to be converted largely to lactate even in the presence of abundant oxygen although the amount of pyruvate diverted into the mitochondria is largely unknown. Hence, a method for imaging actual lactate production by tumors could be highly informative. We report in this work the design of several lanthanide-based shift reagents (SR) that form complexes with lactate and shift the lactate –OH CEST signal to a different frequency far away from water. Given that these SR’s are confined to extracellular space, the resulting lactate –OH CEST signal becomes a specific biomarker of lactate exported from cancer cells. This method offers great promise for imaging lactate production by tumors.