https://youtu.be/71NDP2lytY4
https://battlelog.battlefield.com/bf4/battlereport/show/1/1375573967753043968/1660739540/
Health appears to instantly regenerate two times when it falls below 20%. Not a medic and didn't see a med kit around the area.
there's perks that can heal players if close to vehicles with medics in them.