Magneto-inductive (MI) waveguides are linear arrangements of magnetically coupled L–C resonators that propagate electrical energy at radio frequency without direct connection. To achieve the strong magnetic coupling needed for low-loss propagation, adjacent elements must be in such close proximity that electric coupling arises. In contrast to electric coupling in split ring resonators, the coupling occurs between the inductive tracks of adjacent resonant loops. Parasitic capacitance is demonstrated in flexible magneto-inductive cable, and shown to introduce additional propagation bands above the MI band. Simple models are developed to predict this effect, and strategies discussed to improve high-frequency isolation.