I don't understand the difference in the two and I have been on the one with "Fe" for 10 years and then all of a sudden my doc switched me to the one without it and I am not certain if the nurse just did it by accident or that it makes that big of a difference. I know the one with the "Fe" has 21 days of green bills and 7 of tan ones and the one without the "Fe" only has 21 green pills..but is there any other difference?