As a side note, you might have heard mention that NPCs, including followers, do not statistically level up or scale as your character does.
This means that if you acquired Lydia at say 5 and then level up to level 50, Lydia would still have the skills and health as if she were level 5.
There is however a way to bypass this on the PC and have the game recalculate your follower's (or any NPC's for that matter) skills;
- Open the console and click your follower, a parenthesised number should appear at the top of the console.
- Write 'disable' and press enter, your follower will now disappear. Fear not.
- Close down the console and let the game run for a few seconds.
- Bring up the console again, make sure that the parenthesised number is still at the top of the console, write 'enable'.
Your follower should now pop up again with recalculated stats equal to his/her level.