In most cases the insurance provider will not need to arrange for you to have a blood test, however if the amount that you have applied for exceeds the limits as described below, you will be requested to have a blood test. The cost of the tests are met by the insurer and in many cases they will arrange for a nurse to contact you to make a suitable time/place for this to occur.
In some cases you may also be requested to have a blood test based on your answers to the medical questions on the application form, or if your height / weight measurements are outside of the range specified by the insurance provider.