Health is automatically healed over time as long as there are no open wounds.
The natural recovery rate is at 0.01 every 9 seconds. With 1.00 representing 100% hp.
Each health recovered always comes at 0.01. At fitness level 0 this equals to 1 hp from a total of 100hp.
Sections marked with - means there is no health recovered over time and only the blood loss is stopped.

A single shotgun round ended up with one wound on the abdomen.
The health loss came at a 0.01/5sec
The ordinary health recovery with no wounds is at 0.01/9sec
A single rag at medicine level 0 comes at no health recovered at all.
At medicine level 1 it comes at no health recovery at all
At medicine level 5 it comes at no health recovery at all
A single bandage at medicine level 0 comes at no health recovered at all.
At medicine level 1 it comes at 0.01/46sec
At medicine level 2 it comes at 0.01/23sec
At medicine level 3 it comes at 0.01/16sec
At medicine level 4 it comes at 0.01/11sec (Sometimes it's 11.2 seconds but i'll round it down.)
At medicine level 5 it comes at 0.01/9sec

Strength increases resistance, technically doubling your hp at fitness level 5
Max health is still at 1.00.
A single bandage at medicine level 5 comes at 0.01/9sec
At fitness level 5 it would mean that you recover health at the same amount of time as fitness level 1.
The implication of it is that a fitness level 5 owns a total of 200 hp.
A fitness level 0 owns a total of 100 hp.
So while they take the same amount of time to recover to their max hp, the level 5 fitness technically heals 2hp every 9 seconds.
While the level 0 fitness heals 1hp every 9 seconds.

A single wound on the abdomen results in a health loss of 0.01 every five seconds.
In context, assuming 100hp is your max health. You would lose 1hp every five seconds.
1 minute of bleeding equals to 12hp.

This would imply that every minute you lose 12% of health.
Five minutes would equal to 60% health lost.
And at 8 minutes 20 seconds equals to 100% health lost.

A wound on the head and the abdomen results in a health loss of 0.01 every 1.70 seconds

A single wound on the head results in a health loss of 0.01 every five seconds.

This means that wounds can stack and increase the blood loss.

A single wound on the legs result in a health loss of 0.01 every 2.50 seconds

Wounds on both legs result in a health loss of 0.01 every 1.50 seconds

The only problem i encountered so far is on how i present this information that is easy to understand.
I still have some images i'd like to add once i've edited them.