I have a pendent with the medical symbol and a microfilm inside with MUCH more history than can go on a piece of paper. Also have a card with the same microfilm in my wallet, along with a regular card with vital information. The microfilm can be read with a magnifying glass. It had allergies, medical history, doctors names/numbers, contact info, etc, etc...
If you're serious about wanting your medical information with you, I would suggest looking into it.