Iron Deficiency? please recommend iron supplement.

I just had my annual blood test. the report has just one item out of normal range. Ferritin is 16, in the range of Iron Deficiency. However, my red blood cell count (Hemoglobin) is pretty in the range, 134.

Family doctor asks me to take FALAFer (iron 100ml), but that really upset my stomach. I'd puke when I took it even with food.

Do I need to take iron supplement, is 100ml too much for me?

Thanks a lot for your advise.