Yes it is possible.
and it is normally used in commercial circuits for measuring battery voltage (VB), regulator output voltages (Vcc) depending on the requirements
Its just same as measuring an external voltage
Only difference is that the voltage source is internal in the circuit
For example lets say you are running a circuit @ battery voltage = 12V
and you want to measure battery voltage
So you just use voltage divider and a low pass filter and coonect the signal to the ADC of the microcontroller
then you can know what is the voltage you are getting from your battery