Formic acid is the simplest carboXylic acid, whose chemical formula is CH2O2. It is often used as an antimicrobial/preservatIVe in lIVestock feed. Formic acid can block some of the decay processes in feed, making the nutritional value of feed maintain longer. Under normal circumstances, the physiological concentration of formic acid is low and easy to metabolize, but in the case of methanol poisoning, the concentration can reach 5 mmoL/L. Similarly, long-term eXposure to eXcessIVe levels of formaldehyde can also increase the content of formic acid in blood and urine.