How fast does the human body replace blood, and does it depend on how much you've lost? More specifically, before the invention of blood transfusions, how long would it take someone to bounce back from the various effects of blood loss?
The human body has 5L of blood on average
For a 350mL blood loss (the typical blood donation amount in India), the body can replenish the lost volume (that is, the plasma) in about 24-48 hours. The red cell count is corrected at around 1-2 months. The white cell and platelet count can take around a few days to a week to be replaced. All of these depend upon the individual's nutrition, built and immunity status.
Of course, if you lose too much blood at once, your body will go into hypovolemic shock before it can start its replenishment (generally starts at around 15-20% blood loss) In that case, the patient needs an immediate blood transfusion to survive. So, if your whumpee is in a place and time where blood transfusion is not available, you might not want them to lose more blood than that, because that's likely to be a funeral :D
The various effects of blood loss include dizziness, fatigue, general weakness, palpitations, pallor, shortness of breath, anxiety, uneasiness. Since, the white cells, the ones responsible for fighting off various infections are low during this period, your whumpee might be vulnerable to infections and illnesses they would normally be immune to. Severe blood losses can also cause confusion, disorientation, loss of consciousness.
More specifically, before the invention of blood transfusions, how long would it take someone to bounce back from the various effects of blood loss?
Think about it this way. If your whumpee lost a lot of blood at once, enough to put them in bed, that means the wound to cause that is pretty severe. So how long the whumpee takes to recover depends on the severity of the of the wound itself, the blood loss being a secondary side effect. A minor stab wound, that doesn't injure any major organ, can take several days to a few weeks to recover from. A major stab/bullet wound, with severe hemorrhage, can take up to several months to recover from. Moreover, wound infections can prolong the healing process.
