changing formula brands?

[Snarfle]

hi,
Is swapping over formula brands ok after 2 weeks? will my 4wk old DS be ok? do I phase it in or quick swap?
thanks

I would phase it in. 1 third new/2 thirds old formula for a few feeds, then half/half for a few feeds, then just the new formula. But wouldn't change unless there's a good reason like your DS not tolerating it well.