Systems and methods for controlling measurement units for a medical scale. One system includes a removable head unit configured to couple to a medical scale platform. The removable head unit includes a human machine interface (HMI) and an electronic processor coupled to the human machine interface. The electronic processor is configured to receive, via the HMI, a first user input selecting a permanent lock mode. The electronic processor is configured to, in response to receiving the user input, present a first authentication request and receive a second user input including a first authentication token. The electronic processor is configured to, when the first authentication token is valid, present a measurement unit selection prompt. The electronic processor is configured to receive a second user input selecting a measurement unit and, in response to receiving the second user input, activate the permanent lock mode based on the selected measurement unit.