The molecular virial theorem states that for a diatomic molecule or for an atom in the presence of a point charge, the changes in the average kinetic energy and average potential energy are equal to < T > = -U - R dU/dR and < V > = 2U + R dU/dR, respectively, where U is the interaction energy and R is the internuclear separation or the atom-point charge separation. In this paper we directly evaluate the < T > and < V > expectation values of an H atom in the presence of a distant point charge, obtaining exact analytical expressions by use of Dalgarno-Lewis perturbation theory.