The production of red blood cells is regulated by a feedback loop involving erythropoietin. In non-disease states, the production of red blood cells is equal to the destruction of red blood cells, thus maintaining sufficient red blood cells to deliver adequate oxygen to the body's tissues. However, when the number of red blood cells decrease and oxygen levels are low, erythropoietin is produced by the liver and kidneys to increase the production of red blood cells. Is this a positive or negative feedback loop

Negative feedback.

Explanation:

The production of erythropoietin by the liver and kidneys is a negative feedback because with the production of erythropoietin, our body tends to move to become more stable state. The erythropoietin is produced by the liver and kidneys to increase the production of red blood cells if the quantity of red blood cells are lower than the normal range. If the number of red blood cells are decreases the oxygen level in our body is low that leads to unstable condition of the body but when the concentration of red blood cells increases, the body move towards stability.

not always but somethings can be reproduced in a laboratory.