AutoIncrement Field reaches maximun value?

[Jesus Inzunza]

Hi,

I have a table which saves the registered users in my site. I'm still developing it, and I became worried about the fact that maybe someday the autoincrement id field will reach the maximum value, so I would like to know what can I do today to avoid this scenario.

The id is a MediumInt(5), so I thought that maybe a solution would be that when the id is almost reaching its max, alter it to a MediumInt(6). The problem that I see is that this change will alter other related tables that also got the id in them, or maybe the autoIncrement will not continue counting.

What could be the best approach? Make it MediumInt(6) from the start? (I know, it will be a long time before I reach the 100,000 users, but better be prepared).

Thanks in advances for your comments,

Jesus Inzunza