This study will test whether the drug dapagliflozin is safe and has beneficial effects when added to conventional heart failure therapy in patients who have been admitted to the hospital for acute heart failure. 

Approximately 2400 people will take part in the study and their participation will last 2 months. 

Inclusion Criteria
1. Age ≥18 years (male or female)
2. Currently hospitalized for AHF defined as meeting all the following criteria:
a) Presentation with worsening symptoms of heart failure (e.g., worsening dyspnea or dyspnea at rest, progressive fatigue, rapid weight gain, worsening edema/abdominal distention/anasarca)
b) Objective signs or diagnostic testing consistent with volume overload (e.g., jugular venous distension, pulmonary basilar crackles, S3 gallop, ascites, hepatomegaly, peripheral edema, radiological evidence of pulmonary congestion, noninvasive or invasive hemodynamic evidence of elevated filling pressures)
c) Intensification of AHF therapy during admission defined as at least one of the following:
i. Augmentation of oral diuretic therapy [e.g., ≥2x outpatient regimen dose, addition of a second diuretic agent, or new initiation of diuretic therapy in a previously naïve patient]
ii. Initiation of intravenous diuretic therapy
iii. Initiation of intravenous vasoactive agent (e.g., inotrope or vasodilator)

3. Left ventricular ejection fraction (LVEF) measured within the past 12 months (including during the current hospitalization)
4. Elevated NT-proBNP or BNP during current hospitalization:
a) For patients with LVEF ≤40%: NT-proBNP ≥1600 pg/mL or BNP ≥400 pg/mL (NT-proBNP ≥2400 pg/mL or BNP ≥600 pg/mL if patient in atrial fibrillation or atrial flutter)
b) For patients with LVEF >40%: NT-proBNP ≥1200 pg/mL or BNP ≥300 pg/mL (NT-proBNP ≥1800 pg/mL or BNP ≥450 pg/mL if patient in atrial fibrillation or atrial flutter)
5. Eligible patients will be randomized no earlier than 24 hours and up to 14 days after presentation while still hospitalized once they have been stabilized, as defined by:
a) No increase (i.e., intensification) in the dose of intravenous diuretics during the 12 hours prior to randomization
b) No use of intravenous vasodilators or inotropes during the 24 hours prior to randomization