Lactate, once considered a waste product of cellular metabolism, plays a critical role in immune and inflammatory responses. Recent research highlights its involvement in energy metabolism, signal transduction, and inflammatory processes. This review explores the paradoxical role of lactate in the inflammatory microenvironment, emphasizing lactate homeostasis, the lactate shuttle, and lactylation (the "lactate clock") in acute and chronic inflammation. Lactate influences immune cell function through receptors and affects inflammatory responses by modulating signaling pathways. Lactate metabolism is crucial for immune cell activation, polarization, and function, with implications for both acute and chronic inflammation. Lactate can promote or suppress inflammation depending on the context, and its regulation is essential for maintaining tissue homeostasis. Lactate also plays a role in disease progression, including sepsis and cancer, and its modulation offers potential therapeutic strategies for inflammation-related diseases. Understanding lactate's role in inflammation provides new insights into therapeutic approaches for managing inflammatory conditions.Lactate, once considered a waste product of cellular metabolism, plays a critical role in immune and inflammatory responses. Recent research highlights its involvement in energy metabolism, signal transduction, and inflammatory processes. This review explores the paradoxical role of lactate in the inflammatory microenvironment, emphasizing lactate homeostasis, the lactate shuttle, and lactylation (the "lactate clock") in acute and chronic inflammation. Lactate influences immune cell function through receptors and affects inflammatory responses by modulating signaling pathways. Lactate metabolism is crucial for immune cell activation, polarization, and function, with implications for both acute and chronic inflammation. Lactate can promote or suppress inflammation depending on the context, and its regulation is essential for maintaining tissue homeostasis. Lactate also plays a role in disease progression, including sepsis and cancer, and its modulation offers potential therapeutic strategies for inflammation-related diseases. Understanding lactate's role in inflammation provides new insights into therapeutic approaches for managing inflammatory conditions.