Thank you for contacting BibleAsk.
“And in the eighth day the flesh of his foreskin shall be circumcised” (Leviticus 12:3).
Today’s science has revealed why the eighth day is best to circumcise a baby. Vitamin K is responsible for the production (by the liver) of the element known as prothrombin. If vitamin K is deficient, there will be a prothrombin deficiency and hemorrhaging may occur. It is only on the fifth through the seventh days of the newborn male’s life that vitamin K (produced by bacteria in the intestinal tract) is present in adequate quantities.
Holt and McIntosh, in their classic work, Holt Pediatrics, observed that a newborn infant has “peculiar susceptibility to bleeding between the second and fifth days of life…. Hemorrhages at this time, though often inconsequential, are sometimes extensive; they may produce serious damage to internal organs, especially to the brain, and cause death from shock and exsanguination” (1953, pp. 125-126).
But why did God specify day eight?
On the eighth day, the amount of prothrombin present actually is elevated above one-hundred percent of normal—and is the only day in the male’s life in which this will be the case under normal conditions. If surgery is to be performed, day eight is the perfect day to do it. Vitamin K and prothrombin levels are at their peak. The chart below, patterned after one published by S.I. McMillen, M.D., in his book, None of These Diseases, portrays this in graphic form.
In His service,
The BibleAsk Team