The object of the present invention is to provide a spherical activated carbon that has an excellent adsorbability of uremic substances in a body, in particular β-aminoisobutyric acid. The object can be solved by an adsorbent for oral administration, characterized by comprising: a surface-modified spherical activated carbon having nitrogen atom of 0.5 % or more by weight, a specific surface area determined by BET method of 800 to 3000 m2/g, an average particle diameter of 0.01 to 1 mm, and a total amount of acidic groups of 0.30 meq/g or more.本發明之目的在於提供一種對於活體內之尿毒症性物質、尤其是β-胺基異丁酸之吸附能力優異之表面改質球狀活性碳。上述課題可藉由經口投予用吸附劑而解決，該經口投予用吸附劑之特徵在於包含表面改質球狀活性碳，該表面改質球狀活性碳含有0.5重量%以上氮原子，由BET法所求出之比表面積為800m2/g~3000m2/g，並且平均粒徑為0.01mm~1mm，總酸性基為0.30meq/g以上。
