1year post gastric sleeve surgery, vomited blood. Should I be concerned? Also UC patiant

Because of the high dose cortisol, you are high risk for ulceration. Bleeding could be sign of that and could be dangerous to your health.
Before you suffer from major bleeding or perforation of your ulcer, you should get and Endoscopy to evaluate your stomach, duodenum and Esophagus.
Then you can be treated accordingly!
If bleeding is more than a few drops, you should get medical attention immediately or go to ER. 

You need to get an endoscopy to see what is going on inside your stomach ASAP. This could be serious, so they need to determine if there is an issue or not.