Hi My Friend Has Just Fallen Ill And I Am

Hi my friend has just fallen ill and i am worried i don't know much but he said he didn't feel well and that his stomach was hurting really bad, and that he could barley stand to the point where he just collapses. he has been taking into hospital n i cannot find out whats up with him. If you can please help i would appreciate it loads. he is a 15 year old male