DD is 3 months old, so far exclusively breastfed. She's now being put on a special formula to help her grow as she's failing to thrive and is both lactose intolerant and allergic to cmp. Trouble is she hates the formula and point blank refuses to take it. Her calorie intake is so tiny at the moment, it's very worrying, and we need to get her on the new milk ASAP without her losing any more weight, so I've started pumping feeds for her and hope to start gradually adding formula till she's taking full formula bottles happily.
What I'm wondering is how often and for how long I should be pumping in order to get the right amount for her. We'll hopefully only have to do this for a short while as she adjusts, but I have a toddler, so time is short! I understand she needs an average of 750ml breast milk per day. Is that right? Should I pump at every feed (about every 3 hours) or do longer sessions less often? And does anyone have any tips on what's most efficient in general? I have an Avent single electric pump and don't really want to buy a double since this is likely to be a short term situation.
Thanks 