The effects of adding a sodium–glucose cotransporter 2 (SGLT2) inhibitor to a mineralocorticoid receptor antagonist (MRA) or an angiotensin receptor–neprilysin inhibitor (ARNI) in patients with heart failure (HF) and mildly reduced ejection fraction (HFmrEF) and preserved ejection fraction (HFpEF) are uncertain, even though the use of all three drugs is recommended in recent guidelines. Here, SLC5A2 is linked to heart failure.