Whey protein isolate typically contains less lactose compared to whey protein concentrate, as it is made through further processing to remove more of the lactose and other components from the whey. However, it is not necessarily lactose-free and may still contain small amounts of lactose.
The exact amount of lactose in whey protein isolate can vary depending on the specifics of the manufacturing process, so it is always best to check the ingredient list and label of the specific whey protein isolate product before starting a new dietary supplement regimen. If you are lactose intolerant, it may be advisable to use a non-dairy protein source.