Introducing formula...is my doctor wrong?

So I’m trying to introduce formula to my 1 month old to do combo feeding. After 3 days of 1 bottler per day, he started to get diarrhea so I stopped. The doctor said it could be him getting used to it and try 1oz every 24 hours for a few days. Does this seem right? I feel like that’s putting my baby’s health at risk.