The invention concerns a process for producing lactose-free or substantially lactose-free milk, preferably without addition of water, and the product obtainable by the process. The process comprises the steps of: a) Ultrafiltration of original milk to obtain a first permeate and a first retentate; b) Nanofiltration of said first permeate to obtain a second permeate and a second retentate; c) Mixing said first retentate with said second permeate to obtain a mixture; and d) Hydrolysing remaining lactose in said mixture to obtain a hydrolysed milk. The process provides a lactose-free product with the taste of the original milk.