1 EXHIBIT 23.1 Consent of Independent Auditors We consent to the incorporation by reference in the Registration Statement (Form S-8) pertaining to the 1995 Director Stock Option Plan of GelTex Pharmaceuticals, Inc. of our report dated February 9, 1998, with respect to the financial statements of GelTex Pharmaceuticals, Inc. included in its Annual Report (Form 10-K) for the year ended December 31, 1997, filed with the Securities and Exchange Commission. /s/ Ernst & Young LLP ERNST & YOUNG LLP Boston, Massachusetts July 31, 1998