Quoting *La Mom De Nathan*:" DS turns 13 months on the 28th and I've posted before how he will not eat solids at all! I've tried everything ... [snip!] ... iron levels, his pedi wasn't concerned about it, but the WIC office was. Is poly-vi-sol any good? Do you give it to your LO?"
We used poly-vi-sol when I was breastfeeding, rather than just vitamin D. It was what the NICU doc had recommended. We were happy with it and didn't have any problems getting them to take it down mixed in a bottle.
However, I'm pretty sure you are talking about Fer-in-sol instead. That is the iron supplement! We also used this one. I actually hate it and so do my girls. It has an awful taste and is difficult to get them to take. It also stains everything it touches so when they spit it out it ruins all their bibs, etc. If yours needs the extra iron, you will just have to suck it up though. It can constipate a bit, but you can give prune juice or something to help with that.