Scaling Health Mod 1.13.2/1.12.2 allows adjusting of player and mob health.
This mod will, by default, allow the player to gain extra health. Mobs will also gain extra health, with the amount increasing gradually over time. Both player and mob health increases can be disabled. The rate at which the difficulty increases can also be changed.
A per-player difficulty system. A difficulty value is tracked for each player, increasing slowly as time passes. As difficulty increases, mobs become stronger. For servers, mob strength is calculated based on one of several methods (see below). This feature can be tweaked/disabled.
More player health! Or less. Players can obtain heart canisters that increase their maximum health. Normally, you keep the extra health even after dying (configurable). The player?s starting health can also be changed, and the max health cap is configurable as well.
Lots of control. Plenty of config options to let you play the game however you like! There?s even an in-game config screen, so you can tweak options without restarting Minecraft.