advice please ladies :*

midwives originally prescribed me 3 tablets of iron a day as my levels are low, this was then dropped to 2, then put back up at my last check to 3 as it wasn't stable enough. when I picked my last prescription up, I was given enough until my next midwife meeting (if I took 2 per day) which is Thursday. but as I am back on 3 they run out sooner (think I have like 6 left?) but don't have midwives until Thursday so wouldn't have enough..how do I go about getting more of them on prescription? can my GP do it or does it have to be midwives?