In October, My Hemoglobin Level Was 11.4 G/dL. In The

In October, my hemoglobin level was 11.4 g/dL. In the last few months, I have been light-headed at times, feel weak, have no stamina, tire easily, and struggle to walk more than a block at a time without feeling extremely out of breath. I had a gastric bypass in 2001, and I'm not good at taking my daily vitamins. I suspect I'm suffering from either a Vit B deficiency or an iron deficiency?