Iron levels dropping quickly

Had the same problem with my daughter but this time around, it’s happening even more quickly. Last Monday I had a test done and it was right at 10. Yesterday I had a repeat one done and it’s already down to 9.2 so I’m being put on double the dosage for iron. Definitely want to get it at 12 or higher because I had to get 6 weeks worth of infusions with my daughter and that sucked.

With that being said... what do y’all take to help with constipation? Lmao. Because I know I’m going to run into that problem. I was going to run by the store and grab some miralax but didn’t know if there might be a better option?