My alt is 300 what does this mean?

I am a 29 year old man.

You'd have received more responses had you asked this question in the Health section of Yahoo! Answers, my friend.

Your Alanine transaminase (ALT) level of 300 indicates that you have damage to your liver. This can be caused by a number of things. Take a look at the following web pages to see if you find them useful.

What is alt?