Almost passed out last night. Was it the alcohol?

Anyways I was drunk last night at a friends house. I was laying down on this recliner when I had to use the restroom so I made my way to the stairs. Out of nowhere my balance went and my vision started to black over. Within seconds I was completely blind and a couple friends ran over to grab me. I was pale white and they brought me outside to sit on the porch. My vision came back rather quickly once i sat down. I drank some iced tea and sat outside for a good ten minutes. A few hours later I attempted to go back upstairs and the same thing almost happened. I was able to get myself outside before it got bad though. Anyways what's your opinion on what happened. Alcohol mixed with lightheadedness?