Health | Salt and Sanctuary Wiki

To test health gained per level, I leveled a character from level 1 to 205. The following are the results of my testing. I found that starting at level 1, 5 health is gained every 2.5 levels (rounded up). Beginning at level 40 health is gained every 5 levels. There is never another increase (tested through cheating).
So the list is:
Lv.1 = 100
Lv.3 = 105
Lv.5 = 110
Lv.8 = 115
Lv.10 = 120
Lv.13 = 125
etc ...
Lv.40 = 180
Lv.45 = 185
Lv.50 = 190
ect ...
Lv.200 = 340
Lv.205 = 345
Lv.210 = 350
ect ...
Lv.530 = 670
Lv.535 = 675
Lv.540 = 680

Hope this helps, I noticed there was no in-depth info on health gains.
*note: Increasing your level is the ONLY way to gain permanent health.