- When the device is powered off, press and hold the measurement button for 8 seconds to enter unit switching mode. Under this mode, both Fahrenheit and Celsius should flash at the same time.
- Under this mode, press the measurement button to switch to Fahrenheit or Celsius. The corresponding symbol of the selected unit after switching will flash.
- After selecting the unit, press and hold the measurement button for 8 seconds to leave the unit switching mode.
*credit to Sylvain of iHealth Labs EU
https://helpcenter.ihealthlabs.eu/hc/en-gb/articles/360007270758-iHealth-PT3-Unit-switching