<Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2017) (Learn how and when to remove this template message) </Td> </Tr> <P> Clotting time is the time required for a sample of blood to coagulate in vitro under standard conditions . </P> <P> There are various methods for determining the clotting time, the most common being the capillary tube method . It is affected by calcium ion levels and many diseases . Normal value of clotting time is 8 to 15 minutes . </P> <P> For the measurement of clotting time by test tube method, blood is placed in a glass test tube and kept at 37 ° C. The required time is measured for the blood to clot . </P>

What is the normal clotting time for blood