When to go up a teat size?

[GreyGirl]

My LO just turned 3 months and technically should be using the next size up of teat right? I tried using one a month ago and it flowed out of her mouth, she has a small mouth (thanks to me) and has an upper lip tie and (hopefully) sorted tongue tie. She hardly dribbles now unless tired...
My question is how do you know when they're properly ready to move up a size? Or should I just suck it and see? She's still in 0-3 clothes if that helps.

 

[lch28]

i moved my LO from slow flow to regular flow when i noticed he was takign FOREVER to finish a bottle, and falling alseep half way throuhg from being so tired from sucking. I had tried 2 weeks before this and it all flowed out of his mouth, but 2 weeks later they were great for him. They chanage pretty quick so id give it a go now!

 

[Chris77]

I went to medium flow nipple when PJ was around 5 or 6 months old. I noticed that he was losing interest in his bottles because it was taking him so long to drink them. Once I changed to the medium flow he regained interest.

 

[b4baby]

I change on the day she turns onto the next teat size. Today we are on to teat 3