We claim the ornamental design for a blood glucose meter, as shown and described.
FIG. 1 is a perspective view of the front, left, and bottom sides of a blood glucose meter according to the claimed design;
FIG. 2 is a perspective view of the front, right, and top sides thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof;
FIG. 9 is a perspective view in a state where a lid is opened; and,
FIG. 10 is a reference perspective view in a usage state.
The broken lines in the drawings depict unclaimed environmental subject matter, are for illustrative purposes only, and form no part of the claimed design.