hello good morning hope you are doing good Now lets answer your question step by step Causes of blood during spitting can be due to 1.Gum bleeding which  is most probably happening due to the infection in your gums and that is the first sign which shows that you have a issue with your gums. So i would advice you to go and see a dentist soon. 2. another cause for blood in spit can be because of any recent tooth you  have got it removed so blood can come from that site as well. But most probably the major reason would be the first one. Solution: Go and see a dentist soon and get teeth cleaning done that will solve your all issues regarding the blood in spit and also it will make your gum very healthy and smile a lot more brighter. The whole procedure might last for 30mins to 1hr. and will cost you 600-800 rupees. it was pleasure answering your doubt. keep smiling Warm regards Dr.pranay Smilecure dental clinic bangalore do call on 9916206200 for any more concerns