Duplicate. Please look up existing issues and upvote them instead.

You have to test your blood type, and that of the donating player before iniating a blood transfusion. The reason you went unconscious, is because your blood type and that of the donating player were not a valid match, which caused a blood clot in your veins.

I use this website for reference:
http://www.disabled-world.com/calculators-charts/blood-chart.php

Hope this helps.

All have already been reported, please search before creating new reports.

You should also follow the format specified in the 'How-To' guide at the top of the page.

Thanks.