In this fourth installment of our heart failure series, we dive into another essential pillar of guideline-directed medical therapy (GDMT): the renin-angiotensin system (RAS) inhibitors. This includes ACE inhibitors, ARBs, and ARNIs—cornerstones of treatment for patients with heart failure with reduced ejection fraction (HFrEF). Join us as we unpack how RAS inhibitors work, when to initiate therapy, and how to navigate clinical decision-making around switching, tolerability, renal function, and blood pressure thresholds. We also discuss practical considerations for initiating or holding therapy during acute kidney injury (AKI) and the evidence-based rationale for continuing these agents even with declining GFR. Whether you're managing complex patients in the SNF, at home, or via telemedicine, this episode offers clear, clinically grounded insights to optimize care.