Hypoxia-inducible factor (HIF) is a protein that plays a crucial role in how cells respond to low oxygen levels, a condition known as hypoxia. When oxygen levels drop, HIF activates specific genes that help cells adapt by promoting processes like increased red blood cell production and enhanced blood vessel formation. This adaptation is vital for maintaining cellular function and overall health. HIF is composed of two subunits: HIF-α and HIF-β. Under normal oxygen conditions, HIF-α is rapidly degraded, but during hypoxia, it stabilizes and accumulates in the cell. This stabilization allows HIF to bind to DNA and initiate the expression of genes that support survival and function in low-oxygen environments.