My ef is 18-20. I take the lowest dose of Entresto (24-26) twice a day because I can't tolerate the 49-51 dose. The 49-51 dose made me exhausted and unable to function. I have been on the lowest dose for about 6 months, but I have no improvement in symptoms--still short of breath, no energy. I wonder if I should stop the Entresto; the cost is very high.