This paper presents a coplanar-fed antenna designed to operate close to the human body in the 2.45 GHz Industrial Scientific Medical (ISM) band. The antenna matching is studied in free space and in body proximity. Two models of the human arm, with flat and elliptical cross sections, have been simulated. The results have been compared to measurements in the proximity of a human user with a bare arm and wearing a jacket. It was confirmed that the proposed antenna detunes near the body, but still has acceptable matching performance considering |S11| ≤ -6 dB. Both arm models yield similar results. The simpler flat arm model was found to be sufficiently accurate for reflection coefficient estimations. The simulated Specific Absorption Rate (SAR) is also presented and result values are below regulations for both human models used