The ADC range commonly on most uPs is Vss to Vdd, ie 0 to 5V. Some allow rescaling the range to be narrower than the full supply range, but still usually more than 2V. With a 12bit ADC, the step size would be 5V/4096 ≈ 1mV.
With a standard 50mV/10A shunt, you would only get 50 discrete steps...
You could use a high-side current monitor chip as described in
this post, and scale your current reading such that full-scale=5V, and thereby utilize the full ADC range.