All babies are different, eat differently, and reach different milestones at different times. So, it'll probably come as no surprise that there isn't a set rule for when to introduce bottles to a breastfed baby. There are many factors that you'll need to consider when making this decision.
Some parents introduce bottles to their breastfed babies because they need to return to work. Others might need to give their babies formula because they're taking medications that are contraindicated while breastfeeding. Many moms like to store breast milk and bottle feed it to their babies later, and others need to supplement with formula while they increase their milk supply.
In any case, every parent has a different story, and some might need to introduce a bottle earlier than others. Physicians recommend exclusive breastfeeding until your baby is six months old, but they also advise that the most important thing is for your baby to be well fed. Sometimes, this requires bottle feeding.
If you need to bottle feed your baby from an early age, most doctors recommend that you wait until your baby is at least three weeks old. This will allow them to learn how to breastfeed properly before switching to a bottle. Bottle feeding involves different tongue and mouth movements than those required for breastfeeding. So, if you're planning to go back to work, try starting to bottle feed your baby at least two weeks beforehand. That way, your baby will have enough time to get used to the bottle.