Thank you for the opportunity to help you with your question!
It would drop way down, probably lethally pretty quickly. The conversion back consumes more than is liberated. (creating the lactate releases 2, moving it back to glucose consumes 6)
that is why it is primarily used in nature just for muscle movement when things have gotten a bit on the anaerobic side - the muscle can get decent ATP without having to use local oxygen and turning the lactic acid over into the Krebs cycle, with the conversion back to glucose usually taking place in the liver.
You can refer interactive website that give you basic concept of cori cycle