The present study discusses a scheme to take into account core temperature variation in a well-known bioheat equation. First, the limitation in conventional modeling of the bioheat equation was investigated for a problem in which the whole-body phantom should be taken into account. Then, schemes for varying body-core temperature in the bioheat equation were discussed for radio-frequency exposures. The computational uncertainty in the core temperature elevation was found to be reasonable when a proper scheme for computing the net rate of heat acquisition by blood from body tissue was introduced.