Can eating beets make your stools blood red?

Yes. So can bleeding: Blood in stool is a warning sign. Brisk bleeding warrants emergency care. Causes of bleeding may be predictable (e.G rectal trauma), & worsened by your thrombocytopenia, A rule of thumb (but not absolute): black stool means bleeding comes from upper GI tract; grape jelly stool from small bowel; silver stool from biliary tree; burgundy stool from right colon; red blood from left colon to anus.