View source for Hit Die Adjustment (3.5e Variant Rule)

=== Adjusting Hit Dice by Class Levels ===

At every 7th character level your PC gains, their Hit Die increases by one step. This increase is NOT retroactive, and does not apply to racial hit dice. So a 7th level wizard would now roll a d6 instead of a d4. Then at 14th level, the wizard rolls a d8 instead of a d6. At 21st level it increases one final step to a d10.
 
==== Increases beyond a d12 ====

After a PC's Hit Die increases to a d12, it does not increase further. However, the PC gains an additional +1 hit point per level once another 7 levels have been obtained.
Author	Spanambula +
Identifier	3.5e Variant Rule +
Rated By	BackHandOfFate +, Foxwarrior + and Ghostwheel +
Rating	Rating Pending +
Summary	As you gain experience, you learn how to take more damage. +
Title	Hit Die Adjustment +