Erythroytes (Red Blood Cells)
follow a lifecycle outline here.
Key facts from the article indicate that under normal conditions:
1) 2.5 Million of 25 Trillion or .00001 % of all RBCs 'die' each day
2) Production period for RBC maturity is 4 days
3) RBC Lifespan is 120 days
If we assume that:
* a transfusion brings us up to 100% (25 Trillion RBCs) and
* age of infused and self produced RBCs is evenly distributed
* effectively no new RBC are produced \ infused
I realize that these assumptions may not be realistic, however I would expect that slightly less than 1% (1/120) decline in Hb every day.
Why all the mathematical gymnastics? Well, my dad was diagnosed with MDS and infusions would help but lethargy would set in rapidly afer a few (2-4) days. If a blood infusion results in lethargy\fatigue < 2 days, then either the transfusion did not provide a significant enough RBC boost and \ or something is accelerating RBC deaths (for example Malaria or possibly cytokines)
I like this MDS explanation:
http://www.greghankins.com/gregsmds/The_basics.html