I assumed so as both myself last year and my sister this year were put on high doses of iron post birth for like two months because of blood loss in birth and anaemia and we both were exclusively breastfeeding newborns! Both babies seem fine so assume it's ok!
There was an interesting discussion on iron supplements on inside health on radio 4 last week (I think). A study has found that more iron is absorbed when taking a lower dose every other day. I took spatone when pregnant & BF, mainly due to the prescribed dose making me feel really sick and upsetting my stomach. Turns out, there is no evidence to support the daily dose that's recommended by GPs.