Advice on introducing formula at 3 months

[Happygolucky12]

I have to return to work in 4 weeks time, I plan to introduce a bottle of formula at bedtime and express the milk that I would have given and start storing it up for when I return to work.
I was wandering if anyone has any advice on this or would be willing to share their experience? I am particularly interested to know how much this will alter my babies digestive system/poop and how much formula I should be giving and which is the best formula? I know that it's best to express in the morning - I have done this in the past but I became engorged as it isn't possible for me to do it everyday for various reasons.
My health visitor is very much "breast is best" to the point of being a bully so I don't want to ask for advice as I feed guilty enough already.
Thanks x

I think its really crap that the HV's attitudes are often "breast is best" without accepting the reality of real life and a particular woman's circumstances.

FWIW we use aptamil ready mixed formula and have done since birth when we were just topping him up until now when He is exclusively formula fed. The bottle or Pac has a guide to how much formula to give per feed based on weight however I have seen some on here warn against giving the same volume of formula to an EBF baby as they tend to drink in smaller volumes to FF babies. I would say start with a little less than recommend maybe and then watch to see if baby is satisfied from that or looking for more.

Also most formulas are very very similar (what goes into them is highly regulated) so generally they differ very little, however sometimes those small differences agree more with your baby than other formulas. Main thing is not to keep switching formula as this can lead to stomach upset.

Good luck with it, I hope you find what works best for you and your family.