The cost of a single HCG test is about$80, or if the patient is simply trying to determine if she is pregnant, the HCG test alone; if the patient also wants to determine how active the gestational sac is, it is recommended that both the HCG and progesterone tests be performed, with the progesterone costing about$40 and the two tests costing about$120. It is not possible to perform the test in a single session, but also on alternate days. If the gestational sac is active, the HCG will usually double or increase by at least 60% on the next day of testing. However, the doubling of HCG also depends on the specific value of HCG, which can be doubled on the next day for 0-2000mIU/mL; for 2000-4000mIU/mL, it usually takes about 72 hours to double; for more than 6000mIU/mL, it usually takes 96 hours to double.