Earlier This Evening I Spit Up Three Or Four Clots

Earlier this evening I spit up three or four clots of fresh blood. I did not feel ill then nor do I now,some four hours after the event. I have not coughed blood up before. I am in good health for my age. I really don't want to go to the ER unless it is highly advisable. I'm tired, and I'm pretty sure I would fall asleep quickly, but if a night's delay would be inadvisable, then I will go to the ER. Otherwise, I will call my regular Doctor in the morning and have him look me over. Just before I had the event, I had finished my nightly hour and a quarter hour's walk on my treadmill. Nothing unusual happened to me today.