I went to dentist yesterday. have peronditis. did a cleaning. my upper gum has been bleeding and won't stop. is this normal? how long should this last?

If the bleeding is significant you may want to go for evaluation if the bleeding is ongoing. Gingivitis/Peronditis increase chances of gum bleeding. If it is not much try vitamin C and good oral hygiene to reduce chances of future bleeding. Improved oral hygiene and fluoride use should help and avoid hard bristles in tooth brush. You may also want to avoid like toast hard food to avoid gum injury.

It appears your gums are very swollen due to periodontitis . It should stop bleeding in few hours otherwise go back to dentist and he can stop the bleeding very quickly provided you are not on any blood thinner which you did not fill out in your medical history.

Gum disease[periodontitis] will cause bleeding even after a cleaning. Place warm compress over area and hold it with pressure for 7- 10 minutes. Also can put a warm tea bag over area. Don't brush or irritate area. Rinse with chlorhexidine or peroxide and water for 30 seconds. If bleeding continues, go back to dentist, but follow post cleaning instructions.