Miller, Charles R., c.1846 born; Feb. 15, 1864 pvt., Co. D, 8th Ohio Infantry Rgt. Aug. 27, 1865 discharged for disability at Grafton, WVa.
Source: Official Roster of the Soldiers of the State of Ohio

The regiment was organized from 44th Ohio Infantry Rgt. in January 1864 and served in the Shenandoah Valley and portions of West Virginia. The regiment was mustered out July 30, 1865.
Miller was discharged a month later so I'd guess he had been hospitalized prior to July 30. No indication of the cause.

I did not find him in the pension index