When to size up bottle teat

I use the same bottle brand and I understand what you mean. If your baby struggled to drink more milk, you can change to the nearest next stage teat. But if your baby is comfortable with the current teat, can finish milk without alot of milk dribbling out or choked when drinking, can continue with the teat. You can also try the next stage teat and observe your baby when he/she is drinking milk. So that your baby will not have worsened reflux. Some experimenting / trial & error needed but it'll all be alright 🙂 My baby was comfortable with size 1 teat for quite awhile. She is still using size 2 teat even now when she's already 1 yrs old as she prefers the teat's milk flow.

I sized up when he seems to be taking too long to drink,until keep falling asleep. Drinking too slowly isn't good as well as they swallow more air. I followed the guidelines on the months and it worked well. I'm using M size for my 3.5 mth since he was about 3mths old. M is for 3 months onwards.

When baby starts drinking too long. I didn’t follow the recommended age. LO is 2yo and still on size 4 (tried giving Y teats but she rejected).

My baby is 5 months old n still using 0m+ teats also from Philips avent. So far not fussing and drinking fine hence I have yet to size up.

I upsize when I think baby is ready. Perhaps to a size 2/3 depending on months.