Not always.
According to Virginia State Code Section 46.2-905, bicyclists are to stay to the right when riding less than the normal speed of traffic except to pass other bicyclists or vehicles, to prepare to make a left turn, when necessary to avoid conditions (including fixed or moving objects, surface hazards, or substandard width lanes too narrow for a bicycle and vehicle to travel side by side) that make it unsafe to continue along the right.
Moving to the left in the lane to avoid car doors, for instance, even if it means taking the entire lane, is permitted by the State Code.