An object of the present invention is to provide surface-modified spherical activated carbon exhibiting excellent adsorption capacity for uremic substances in the body, and particularly β-aminoisobutyric acid.Accordingly, provided is an orally administered adsorbent comprising surface-modified spherical active carbon containing not less than 0.5 wt% of nitrogen atoms, having a specific surface area determined by the Brunauer-Emmett-Teller (BET) method of 800 m2/g to 3000 m2/g, having an average particle size of 0.01 mm to 1 mm, and having a total acidic group content of not less than 0.30 meq/g.
