Purpose The aims of this study were to examine sex differences in a heart failure population with regards to treatment and patient characteristics and to investigate the impact of sex on achieved doses of heart failure medications. Methods and results A total of 1924 patients with heart failure in a regional hospital were analysed, 622 patients had ejection fraction ≤ 40% of which 30% were women. In patients with reduced ejection fraction, women were older (79 ± 11 vs. 74 ± 12 years, P < 0.001), had lower body weight (70 ± 17 vs. 86 ± 18 kg, P < 0.001), lower estimated glomerular filtration rate (eGFR) (49 ± 24 vs. 71 ± 30 ml/min, P < 0.001) and received lower doses of heart failure medications than men. Multivariable linear regression on patients with reduced ejection fraction showed that sex was not associated with achieved dose of any heart failure medication. For angiotensin-converting enzyme inhibitors and angiotensin receptor blockers associated factors were eGFR, systolic blood pressure, age, ejection fraction, and heart rate. For beta-blockers associated factors were body weight, atrial fibrillation and age. For mineralocorticoid receptor antagonists associated factors were eGFR, serum potassium, age, systolic blood pressure, ejection fraction and heart rate. Conclusion Women with heart failure and reduced ejection fraction were prescribed lower doses of heart failure medications, were older, had worse renal function, and lower body weight than men. Sex was not independently associated with achieved doses of heart failure medications, instead age, renal function and body weight explained the differences in treatment.