I Have Fainted Before

It's only happened 1 time. I was in nursery (kindergarten to Americans) so I was about 3 or 4. I don't remember all of it but I remember feeling something I'd never felt before. I had no idea what it could be or what to do, I was so tired and my head was all fuzzy, it felt like someone was pulling me downwards. I must have fainted then. I woke up and I was lying on the cloak room floor with the teachers running around me. They gave me a juice box and an ambulance arrived with my mum. Then I started crying when I saw her because I thought I was in trouble. The paramedic checked my blood sugars and said they were really low, so he gave me some dextrose tablets and then took me to hospital. They did all kinds of tests on me but found nothing wrong, I was even kept in overnight. It's never happened again but its weird to think about