Help with Formula Transition

[Jem]

Breastfeeding and even pumping have been going wonderfully with DS2, but unfortunately his stomach and skin issues have just gotten to the point where we really need to transition him to formula. He has been prescribed Elecare and after much hoop-jumping we finally have it.

He will not drink it. He wouldn't drink it on it's own and through some experimenting found the only mixture he would tolerate was 0.5oz formula and 4.5oz BM. We've done this a few times and it has generally been successful (he cries a little when he seems to get a gulp of formula but is okay with finishing the bottle). Now I've tried to move to 1oz formula and 4oz BM and he won't do it. Trying another formula is not really an option because it was SO difficult to even get this one (coordinating dr., 3rd party, insurance, etc.). At this rate it will take us the next 6 months to transition. This is feeling incredibly hopeless. Any tips? He is 5 months old in case that matters.

[Velar Fricative]

Have you offered it to him in different temperatures? DD was flexible with room temp vs. cold but some babies prefer one over the other if you haven't tried both yet.

[Deleted]

Are you heating up the formula? DD will still only take formula if it is warm.

[Deleted]

Does he need a different kind of bottle?
I've met more kids who weren't necessarily picky about the formula but definitely had a bottle preference.
change up the temp as well

[Jem]

Thanks all for the responses. He is good about bottles because I've been back at work for 2 months and he has no problem with bottles during that time (they have been BM bottles though). I will try to warm it up. He is fine with whatever temp for his regular bottles, but maybe a warm bottle would make the formula more tolerable.