Often, courses for biomedical engineering combine knowledge of basic science with the applied science of engineering. Depending on the form of biomedical engineering, you'll want to generall concentrate on your engineering courses or the basic science courses more.
If you're aiming more for the biomaterials/bioengineering, you'll want to get pretty strong on the biology side of biomedical engineering. For this, you'll need to take courses like general chemistry and biology, organic chemistry, biochemistry, cell and molecular biology, physiology, and other related courses depending in your specific interest.
If you're thinking more on the engineering side (biomechanics like those who make bionic limbs, heart pumps, and what-have-you) you'll still want some of the biology courses, but you'll need to concentrate more on the engineering side by taking certain courses like mechanical engineering (statics, dynamics, fluids, etc.) and electrical engineering (analog/digital circuits, microprocessors, programming, etc.).
Often, specific schools have specific criteria that must be met to get a degree in biomedical engineering, and you'll have to look at the schools individually to determine whether their requirements line up with what you want to do as a career.