Dear Luke, there is a chance that this sign could mean something serious but dont be concerned untill you do further diagnostic test. It s important to know do you vomit blood, coughing up blood or you just noticed it in your saliva. The first one means that you have some serious gastritis
,gastric ulcer or esophageal disease
. Coughing up blood is also a serious symptom which could be sign of pneumonia
, COPD or even cancer so this needs to be ruled out. Blood in the saliva could be seen due to some lesion (ulcer, tumor
, teeth disorders) of mouth or pharyngeal mucosa. So depending on what I ve just said you should definitely do gastro, pulmo and ORL examination.
Wish you good health, Dr. Ivan Romic (Rominho)