Trying to switch from Enfamil Premium Infant to Gentleease at 3 weeks?

You need to give her AT LEAST a full week on the new formula. Give her time to get used to it before changing things again. Some doctors even suggest staying on the same formula for 3 weeks to see how it works before switching. It's very hard on their stomachs switching around that much so keep her on the gentleease for a while.