In 65 people with heart failure and a preserved ejection fraction, one intravenous iron dose raised peak oxygen uptake at 12 weeks

What the research found

Circulation published a double-blind randomized trial on 8 November 2026. Gregory D. Lewis, Rajeev Malhotra, and colleagues enrolled people with heart failure and a preserved ejection fraction who also had iron deficiency, defined as ferritin under 100 ng/mL or under 300 ng/mL with transferrin saturation under 20 percent. Enrollment ran from December 2021 through April 2026. 44 people received one intravenous dose of ferric derisomaltose, 1000 mg, and 21 received placebo. Median age was 68 years (IQR 58 to 76), and 72 percent were women. 64 of 65 people finished the 12-week visit. Median baseline peak oxygen uptake was 12.7 mL per kg per minute (IQR 10.6 to 15.8) with iron and 12.2 (11.6 to 14.6) with placebo. At 12 weeks, peak oxygen uptake rose by 1.2 (95 percent CI 0.6 to 1.7) with iron and was unchanged with placebo, 0.1 (-0.7 to 0.9). The least-squares mean difference was 1.1 (0.2 to 1.9, P = 0.02). Oxygen uptake at the anaerobic threshold, 6-minute walk distance, and New York Heart Association class also moved in favor of iron (all P under 0.05). The Kansas City Cardiomyopathy Questionnaire overall summary score did not differ (iron +4.4, -2.4 to 11.2, P = 0.20). Transferrin saturation rose by 9.4 percentage points (4.9 to 13.9) and ferritin by 183 ng/mL (128 to 238) versus placebo. No serious adverse event was tied to the iron dose. The trial conclusion is that this iron dose improved several measures of exercise capacity. Ferric derisomaltose is a prescribed intravenous product. This card does not say anyone should start it. Registration NCT04945707. DOI 10.1161/CIRCULATIONAHA.126.084009. Not medical advice. Not a substitute for a prescribed medicine. Off-label prescription use is clinician-only. VitaLonga does not diagnose, treat, or cure disease. Never start, stop, or replace a prescription with a supplement on the basis of a headline.

Evidence level: Clinical trial. This is among the stronger kinds of evidence, but one study rarely settles a question.

Read the original at Circulation